Q1) What is Power BI Desktop application?

Power BI Desktop is an application that can be installed. This works nicely with Power BI by providing
data exploration and shaping and creating report with quality visualization. You can save your work to a
file and publish your reports in Power BI site.

Q2) What data sources can Power BI connect with for data exploration?

Files(XLSX & CSV)

Content Packs

Connectors to databases and other datasets such as Azure & SQL etc.

Q3) What are content packs?

They are collection of related documents and files that are stored as in a set.

Q4) What are all the types of Content packs?

Two types of content packs.

a. Services providers like Google Analytics, Market.

b. Salesforce Shared by other users in your organization.

Q5) What are Building Blocks in Power BI?

 Visualizations
 Datasets
 Reports
 Dashboards
 Tiles

Q6) What is Visualization?

Visualization is a visual representation of dataset that extracts information from the data based on the
business.

Q7) What is report in Power BI?

Report is basically a collection of visualization charts that appear together on one or more pages within
power BI.

Q8) What is Dashboard in power BI?

Dashboard is single layer presentation sheet of multiple visualizations reports.

Q9) What is Tiles in power BI?

Tiles is basically a single visualization in a report or on a power BI dashboard.

Q10) What are all the different types of filters available in Power BI Reports?

 Visual-level Filters
 Page-level Filters
 Report-level Filters

Q11) What is Visual level filter?

Visual level filters works on only an individual/single visualization, reducing the amount of data that the
visualization can see in power BI.

Q12) What is page level filter?

Page level filters work at the report-page level in power BI. Multiple pages in the same report can have
multiple page-level filters.

Q13) What is report level filter?

Report level filters work on the entire report within power BI project. Filtering all pages and
visualizations will include within the report.

Q14) What are all the parts of Power BI?

 Power BI is a cloud-based business service.

 Excel BI Tool Kit
 Power Query
 Power Pivot

Q15) What is Power BI is a cloud-based business service?

Power BI is a cloud-based business service enables the client to interpret information with higher
efficiency and execution.

Q16) What is Excel BI Tool Kit?

The Excel BI Toolkit comprises of Excel and four add-ins that enable us to do the transfer function, shape
transform, create, and to show our analyses.

Q17) What are all the types of Data Refresh Options available in Power BI?

 Package refresh
 Model or data refresh
  Tile refresh
 Visual container refresh

Q18) What is DAX in power BI?

DAX(Data Analysis Expression) do basic calculation and data analysis on data in power pivot. DAX is a
formula language used to compute calculated column and calculated field within power BI.

Q19) Where we can apply DAX functions?

 DAX works on column level values.

 DAX can’t modify or insert data.
 DAX can create calculated column

Q20) Mention some of the most common DAX Functions used?

 SUM
 MIN
 MAX
 AVG
 COUNTROWS
 DISTINCTCOUNT
 IF
 AND
 OR
 SWITCH

Q21) What is unique about the CALCULATE functions?

This is the only function that allows us to modify filter context of measures or tables.

Q22) What is the default visual interaction?

 The DVI is “Drill Mode On”. In the event, we keep it off, we need to change those settings
without fail. Rather set the Default to ‘Drill Mode On’.
 Drilling Mode will be on, if the aggregates are at initial level.

Q23) What are all the connectivity modes available?

 Import
 DirectQuery

Q24) What is Power Pivot?

Power Pivot helps in analysing our data. It empowers users to import large scale of data from numerous
data sources into a single Excel sheet for better users interface.

Q25) What are all the benefits of using variables?

Variables will make unconstrained DAX expressions which are consistent to interpret with data.
Variables can’t be shared among queries or be characterized at the model level.

Q26) what are the ways to create a bar chart?

Drag any one measure into the worksheet and drag one more dimension along it. Now you go to the
show me pane, and choose the bar chart tile. it can be both vertical and horizontal

Q27) What are the types of Data Refresh in Power BI?

By choice there are 4 different types of refreshes that can happen. They are,

 Package refresh
 Model or data refresh
 Tile refresh
 Visual container refresh

Q28) What is DAX?

For basic calculation and data analysis on data in power pivot we can use DAX. It is a formula language
to compute calculated columns and calculated fields.

 Pros and cons of Dax

 Dax works on multiple column values and Dax cannot modify or insert data
 We can calculate calculated column and measures, but we cannot calculate using rows.

Q29) Write a Sample formula for DAX syntax:

For the measure named Total Sales, calculate = SUM of values in the [SalesAmount ] column.

 Measures
 equal signs
 DAX syntax
 Parenthesis
 Reference Table and
 Column name

Q30) Do I need to sign up with my work email?

It does not support email addresses provided by regular email services or telecommunications
providers. So you should sign up using your professional address.

List the work email addresses that are supported.

Working email addresses ending in .edu and .org are always supported.

Those ending in .gov are not currently supported.

Q31) What is xVelocity in-memory analytics engine?

The main engine, xVelocity in-memory analytics engine. This machine can handle large amount of data
as it stores data in columnar databases and in enhances memory analytics which results in faster
processing of data as it loads all data to RAM memory.

Q32) Is Power BI available within campus?

No, Power BI is not available as a private or an internal cloud service. However, with Power BI and
Power BI Desktop you can connect to your own on-premises data sources. With the On campus Data
Gateway, you can connect to your on campus SQL Server Analysis Services server as well.

Q33) Where else can we view on-premises?

 SQL Server with the Power BI iOS.

 SQL Server on the iPhone.
 SQL Server on the iPad.

Q34) What are the Power BI mobile devices?

Power BI has its own apps for Android phones, iOS devices, and Windows 10 devices. Download Power
BI apps from below:

 Apple App Store

 Google Play and
 Windows Store

Q35) What are the Connectors to databases and other datasets?

Azure SQL Database and SQL Server Analysis Services.

Q36) What are the Organizational content packs?

BI professions and system integrators use this tool to build their own content packs to share purpose-
built dashboards, reports, and datasets within their organization.

Q37) What are the different BI add ins?

 Power Query
 Power Pivot
 Power View
 Power Map
Q58) State the differences between Direct Query method and Import method.

Direct Query method Import method

Import method also does data transformation and
Data manipulation is much limited in this method manipulation tasks. If the data is published in PBI, it
and the data will be present in the SQL DB. is limited to 1 GB. Here the data will be present in
Power BI Azure.
As the name implies, the queries are direct and Import method requires to schedule refresh and
does not requires refresh scheduling. has to be refreshed 8 times in a day.

Q59) State the advantages of Direct query method.

Following are the advantages of Direct query method:

 User can build larger data sets data visualizations through Direct query method, but Power BI
desktop supports data visualizations on smaller data sets alone.
 There is no dataset limit for Direct query method and 1 GB dataset limit is not applicable in this
method.
 User can visualize current data report alone while using direct query.

Q60) State the limitations of Direct query method.

Following are the limitations present in Direct query method:

 User can perform data aggregation for unlimited number of rows but returning data is limited to
1 million rows alone.
 All the tables have to come from a single data base only.
 While using complex queries, the query editor returns an error. This error has to be removed
before running a new query.
 Relationship filtering can be allowed only in one direction while using Direct query method.
 There is no support for special treatments in direct query method for time related data present
in the tables.

Q63) What do you mean by DAX?

DAX is the Data Analysis Expression which is used to perform data analysis and primary calculations of
data in the Power pivot. DAX performs math computing through formulas. It works on column values
and calculated field but cannot work on rows. Also, DAX will not alter a data or insert a new data.

Q67) How do you create calculated columns in Power BI?

By joining two or more elements present in the existing data, users can build calculated columns in
Power BI. Users are allowed to define new metrics by stating math calculations in an existing column.
They are also allowed to join two columns to make it as one single column.
Q87) State the list of aggregate functions and counting functions in DAX?

Some of the aggregate functions present in DAX are: Average, Min, Max, Sum and SumX. Some of the
counting functions available are: Count, Distinct Count, Count Rows, Count Blank and CountA.

Q88) What are the calculation types available in DAX?

Power BI allows the users to build two basic calculations using DAX: Calculated measures and Calculated
Columns.

Q89) What are the logical and date functions available in DAX?

Logical functions: AND, OR, NOT, IF and IF ERROR

Date functions: Hour, Date, Weekday, EOMonth and Now.

Q90) What are the information and text functions available in DAX?

Information functions: ISTEXT, ISNONTEXT, ISBLANK, ISERROR and ISNUMBER.

Text Functions: Search, Fixed, upper, concatenate and Replace.

Q93) Tell me about REST API and its association with Power BI.

REST APIs are used to operate the data present in Power BI in real time environments. With the
combination of REST API with Power BI, user can build dashboards, datasets, add/delete rows and can
receive groups. This Power BI REST API can be built through many technologies. Some of them are :

 Ruby
 .Net
 JQuery

Users require Azure active directory token to get access applications in Power BI dashboards.

Q97. Mention some of the Power BI components?

There are different Power BI components namely

 Power Pivot (for in-memory tabular data modeling)

 Power Map (for 3D geospatial visualizing)
 Data Management Gateway
 Power BI Mobile (For iOS, Android, and Windows phones)
 Power Query(for transformation and data mash-up)
 Power View(for data visualizations view)
 Data Catalog
 Power Q/A (for natural language Q/A)
 Power Bi Desktop(a companion development tool)
Q107. What are the formats available for Power BI?

 Power BI Service: An online Software as a Service (SaaS)

 Power BI Desktop: For desktop computers
 Mobile Power BI apps: For Android and iOS devices.

Q108. Mention the work email address supported currently?

Your work email address should end with .edu or .org.

Q110. What do you mean by DAX and explain its basic concepts?

DAX is derived as Data Analysis Expression, which is a group of constants, operators, and functions used
in formulas to return and calculate values. In short, they are used to develop new information from the
existing data. There are three basic concepts included in DAX namely

 Functions: This type of concept use particular values, otherwise called as arguments in the right
order to execute a calculations, just identical to Excel functions. The categories included in the
functions are time intelligence, logical, statistical, parent/child, date/time, information,
mathematical, text, and more.
 Syntax: This indicates the writing format of a formula. It indicates the elements used to
comprise it. The function in Syntax is SUM. You will get an error message in case your syntax is
wrong.
 Context: Filter context and row context are two types of context. Row context is used when a
formula include a function that is used to apply the filter to pick the single row in a single table.
The filter context is used when there is a number of filters applied in a calculation that indicates
a value or result.

 Interactive reports authoring.

Q116. Where are the data of Power BI stores?

All the imported Power BI data from various sources of data are stored in either Dimension tables and
Fact tables.

 Dimension table: It’s a database table that holds every attribute values for the stored data in the
fact table. It held in a star schema that is attached to the fact table.
 Face table: It is the primary or central table of any start schema. It holds the quantitative or
measured values. It contains the primary keys and these are not normalized usually.
Q118. What are the data types supported by DAX?

Data Analysis Expression supports the following data types.

 Boolean
 String
 Numeric
 Decimal
 Datetime

Q120. What you mean by Grouping and how to use it in BI?

Power BI Desktop enables the users to group the data into smaller chunks. You need to use Control +
click to select different elements in the visual for the grouping purpose. You can right-click on any of the
elements, that appear in the groups’ window.

Q122. What is the language used in Power Query?

M-Code is the language used in Power Query. It’s a new programming language developed to be user-
friendly, case sensitive and it’s identical to other languages.

Q123. Mention some of the data shaping techniques?

 Adding Indexes
 Removing rows and columns
 Applying for a Sort order

Q124. Are there any prerequisites to connect to a database in Azure SQL Database?

Yes, you need to configure the firewall settings to enable remote connections before connecting it to the
database in Azure SQL Database.

Q125. Mention some of the advantages of using variables in DAX?

 Variables are capable of making DAX expressions more logical.inituitive to interpret.

 By evaluating and declaring a variable, it can be reused at different times in the DAX expression,
it means you can avoid any of the extra queries of the source database.
 Variables are designed to query or measure. They are not able to share them with the model
level.

141. Explain about Responsive Slicers?

You can easily adjust the responsive slicers according to the required sizes and shapes and the data
contained in a report should be realigned according to it.
145. List the most commonly used DAX functions?

Below mentioned are some of the most commonly used DAX functions:

 SUM, MAX, AVG, MIN, DISTINCTCOUNT, COUNTROWS.

 IF, SWITCH, OR, AND,
 ISFILTERED, ISBLANK, ISCROSSFILTERED
 FILTER, VALUES, CALCULATE, ALL,
 INTERSECT, UNION, NATURALINNERJOIN, EXCEPT, NATURALLEFTEROUTERJOIN, ISEMPTY,
SUMMARIZECOLUMNS,
 GEOMEAN, DATEDIFF, MEDIAN,
 VAR (Variables)

152. List some of the common Power Query Transformations?

The common Power Query Transformations include Filtering Rows, Changing Data Types, Grouping,
Removing Columns, Adding New Columns, Splitting columns, etc.

153. Can we use SQL and Power Query together?

Yes, we can use them together. A SQL statement can be used as a source of Power Query for making
additional logical processing. This will help in ensuring that an efficient query is passed to the source
and avoids unnecessary complexities.

Q156. Explain the Components of Power BI?

Power Query: The ETL (Extract, Transform & Load) Part of the BI is taken care of in Power Query. It is a
Data Transformation Engine. It allows us to Connect a range of information sources ranging from Excel
to Streaming data.

Power Pivot: The Data Modelling Part of the BI Process is performed with the assist of Power Pivot. The
Relationships between the tables are hooked up right here and Calculations are written via Power Pivot
Part of Power BI. It makes use of DAX (Data Analysis Expressions) language to mannequin the data.

Power View: It lets to create Powerful visuals, charts & Graphs from the tables. It can join to the records
sources accessible in the Models and lets you to filter information for every visual or a web page or a
complete report.

Power Map: The Geographical information can be visualized by the usage of Power Map and it used
Microsoft Bing to get the Best visuals primarily based on Latitude and Longitude, Country, State, County,
City, etc.

Power BI Desktop: It is a single device Integrated with Power Query, Power View , Power Pivot and
Power Maps.
Q161. What is the distinction between Measure and Dimension?

Measures: The Measure are used to calculate aggregations such as Sum, Min, Max, Average & Count at
the desk level. It is calculated at the time of the question which says that the Measures are no longer
saved somewhere in the database or in the model. They truely exist.

Calculated Column: The Primary distinction between the measure and the calculated column in the
Evaluation context. The Evaluation of a calculated columns is completed at the row degree the place as
the comparison context of a measure is at the desk level.

Summary:

 Use a calculated column when you choose to consider every row.

 Use a measure when you want an aggregate.

Q164. Explain Bookmark in Power BI?

Bookmarks are sort of Shortcut used in Power BI to navigate to a sure web page that is configured at a
factor of time. We can toggle between a foremost file web page and a bookmark for handy comparison.
Bookmarks are static and all the filter or interactions which are configured won’t exchange till we edit
the bookmarks.

Q171. What are the exclusive roles accessible in Power BI Service?

 Admin
 Contributor
 Member
 Viewer

Q172. What is Cardinality?

Cardinality capacity the relationship which is set up between two tables in the Modelling view of Power
BI. We can discover if the tables have awesome of multi cases per price for the becoming a member of
columns between the two tables.

Q173. What are the exceptional Cardinalities reachable in Power BI?

 One to One
 One to Many

Q174. What is the issue in phrases of Size of Data in Power BI Premium and Power BI Pro?

In Power BI Pro we can cope with up to 1Gb of statistics & in Power BI Premium we can Handle 10 Gb of
Data per User.
70. State the difference between Count and CounD function.

Count function returns to count, excluding NULL values whereas Countd returns distinct values which
exclude NULL values.

74. What does DATEDIFF function do?

This function gives a difference between 2 dates based on the specified Date part.

76. What is IFNULL function?

If the value is not NULL iFNULL function result is the first expression, if it is not, then it will return the
second expression.

77. What is the use of INDEX Function in Power BI?

INDEX function helps you to retrieve the index of the respective row.

78. What is the main difference between LTRIM and RTRIM?

LTRIM function helps you to remove the white space from the LEFT of the string. RTRIM helps you to
remove it from the right the last index.

79. What is the use of MID function?

MID function returns the string character from the specified index position.

80. How can you apply percentile function in Power BI?

PERCENTILE function allows you to returns the data value of the specific percentile number.

81. What is the SIGN function?

Sign function returns the direction of the values. If it returns 1, if positive then 1, if 0 then 0.

83. What is the use of split function?

SPLIT function is used to split the string database on the given delimiter.

86. In which year Microsoft invented Power BI Embedded?

In, the year 2016 Microsoft discharged new administration which is named as Power BI Embedded.

87. What area do you go to change and reshape data in Power BI?

Data Editing helps you to change and reshape data in Power BI.
88. Data Category settings should be used for mapping information to geographic areas in Power BI?

Scope and Longitude (e.g. 47.6080, - 122.3351)

89. What do you use as a consolidate inquiry in Power BI?

Join Queries are used as a consolidate inquiries in Power BI

90. What is the option to unpivot data in the question proofreader?

Unpivot line is a choice to unpivot any data in the question proofreader.

91. What is the process to refresh Power BI reports when it is uploaded into the cloud?

Power BI, reports can be refresh using Data management, gateway, and Power BI Personal Gateway.

92. What visual would you need to use to show solitary esteem?

Disseminate Plat is a visual you should use to show solitary esteem.

97. What context style is allowed by Power BI DAX?

Power BI DAX content style is both Row and Filter.

98. In, Power Bi, where do you discover the Q&A highlight?

You will get at the highest point of a report in the Power BI benefit.

99. How can you dynamically change the value measure to show multiple measures?

You can do this by using harvesting measure and switch function.

Question 2. Explain When Do You Use Sumx() Instead Of Sum()?

Answer : When the expressions to SUM() consits of anything else than a column name.

Typically when you want to add or multiply the values in different columns:

SUMX(Orderline, Orderline[quantity], Orderline[price])

SUMX() first creates a row context over the Sales table (see 1 above). It then iterates through this table
one row at a time. SUM() is optimized for reducing over column segments and is as such not an iterator.

Question 3. What Do You Understand By New Calendarauto() Function In Dax(ssas)?

Answer : CALENDARAUTO function returns a table with a single column named “Date” that contains a
contiguous set of dates. The range of dates is calculated automatically based on data in the model.
Example: In this example, the MinDate and MaxDate in the data model are July 1, 2010 and June 30,
2011.

CALENDARAUTO() will return all dates between January 1, 2010 and December 31, 2011.

CALENDARAUTO(3) will actually return all dates between April 1, 2010 and March 31, 2012.

Question 4. Name Any 3 Most Useful Aggregation Functions Dax?

Answer : DAX has a number of aggregation functions, including the following commonly used
functions:

 SUM
 AVERAGE
 MIN
 MAX
 SUMX (and other X functions)

These functions work only on numeric columns, and generally can aggregate only one column at a time.
However, special aggregation functions that end in X, such as SUMX, can work on multiple columns.
These functions iterate through the table, and evaluate the expression for each row.

Question 6. Name Any 3 Most Useful Text Functions In Dax?

Answer : The text functions in DAX include the following:

 CONCATENTATE
 REPLACE
 SEARCH
 UPPER
 FIXED

These text work very similarly to the Excel functions that have the same name, so if you're familiar with
how Excel handles text functions, you're already a step ahead. If not, you can always experiment with
these functions in Power BI, and learn more about how they behave.

Question 8. What Is The Difference Between Distinct() And Values() In Dax?

Answer : Both count the distinct values, but VALUES() also counts a possible implictit virtual empty row
because of non matching values in a child table. This is usually in a dimension table.

Question 9. Which Function Should You Use Rather Than Countrouws(distinct())?

Answer : DISTINCTCOUNT()
Question 10. What Is A Pattern?

Answer : A pattern is a general reusable solution to a commonly occurring problem.In Microsoft Excel,
you use patterns every day to build tables, charts, reports, dashboards, and more.

Question 14. How Does Calculate() Result In Context Transition?

Answer : When in row context it transitions to filter context: the filter on the rows of a specific table
propagates through the relationship to the related before the calculation is completed.

E.g. CALCULATE(SUM(OtherTable[column]) in a calculated column.

It extends or modifies an existing filter context, by adding a filter as its second parameter.

CALCULATE() always introduces filter context.

Question 15. What Is The Difference Between Max And Maxa Functions In Dax?

Answer : The MAX function takes as an argument a column that contains numeric values. If the column
contains no numbers, MAX returns a blank. If you want to evaluate values that are not numbers, use the
MAXA function.

Question 16. How Are Row Contexts Created?

Answer :

1. Automatically in a calculated column

2. Programmatically by using iterators.

Question 17. How Are Filter Contexts Created?

Answer :

1. Automatically by using fields on rows, columns, slicers, and filters.

2. Programmatically by using CALCULATE()
3.

Question 18. How Can You Propagate Row Context Through Relationships?

Answer :

Propagation happens manually by using RELATED() and RELATEDTABLE(). These functions need to be
used on the correct side of a one-to-many relationship: RELATED() on the many side, RELATEDTABLE()
on the one side.
Question 19. How Does Summarizecolumns Relate To Filtering?

Answer :

1. SUMMARIZECOLUMNS is not susceptible for outer (external) filters, in contrast to SUMMARIZE

2. you can add a filter (e.g. using FILTER) as a param of SUMMARIZCOLUMNS and it will filter
accordingly. It acts as if you've added a filter in a pivot table.

Question 20. What Is The Initial Filter Context?

Answer :

The initial filter context comes from four areas of a pivot table:

1. Rows
2. Columns
3. Filters
4. Slicers

It is the standard filtering coming from a pivot table before any possible modifications from DAX
formulas using CALCULATE().

Question 21. Why Don't You Use A Calculate() In The Aggregation Expression Of A
Summarizecolumn()?

Answer : The CALCULATE() is automatically generated.

Question 23. Dax Nested Functions Is Equivalent To Sql What?

Answer : SQL subqueries.

SQL Interview:

Q5. What are joins in SQL?

A JOIN clause is used to combine rows from two or more tables, based on a related column between
them. It is used to merge two tables or retrieve data from there. There are 4 types of joins, as you can
refer to below:
  Inner join: Inner Join in SQL is the most common type of join. It is used to return all the rows
from multiple tables where the join condition is satisfied.

 Left Join: Left Join in SQL is used to return all the rows from the left table but only the matching
rows from the right table where the join condition is fulfilled.
 Right Join: Right Join in SQL is used to return all the rows from the right table but only the
matching rows from the left table where the join condition is fulfilled.
 Full Join: Full join returns all the records when there is a match in any of the tables. Therefore, it
returns all the rows from the left-hand side table and all the rows from the right-hand side table.

Q6. What is the difference between CHAR and VARCHAR2 datatype in SQL?

Both Char and Varchar2 are used for characters datatype but varchar2 is used for character strings of
variable length whereas Char is used for strings of fixed length. For example, char(10) can only store 10
characters and will not be able to store a string of any other length whereas varchar2(10) can store any
length i.e 6,8,2 in this variable.

Q7. What is a Primary key?

  A Primary key in SQL is a column (or collection of columns) or a set of columns that uniquely
identifies each row in the table.
 Uniquely identifies a single row in the table
 Null values not allowed

Example- In the Student table, Stu_ID is the primary key.

Q8. What are Constraints?

Constraints in SQL are used to specify the limit on the data type of the table. It can be specified while
creating or altering the table statement. The sample of constraints are:

 NOT NULL
 CHECK
 DEFAULT
 UNIQUE
 PRIMARY KEY
 FOREIGN KEY

Q9. What is the difference between DELETE and TRUNCATE statements?

DELETE vs TRUNCATE

DELETE TRUNCATE

Truncate is used to delete all the rows from a

Delete command is used to delete a row in a table.
table.

You can rollback data after using delete statement. You cannot rollback data.

It is a DML command. It is a DDL command.

It is slower than truncate statement. It is faster.

Q10. What is a Unique key?

 Uniquely identifies a single row in the table.

 Multiple values allowed per table.
 Null values allowed.

Apart from this SQL Interview Questions blog, if you want to get trained from professionals on this
technology, you can opt for structured training from edureka!

Q11. What is a Foreign key in SQL?

 Foreign key maintains referential integrity by enforcing a link between the data in two tables.
  The foreign key in the child table references the primary key in the parent table.
 The foreign key constraint prevents actions that would destroy links between the child and
parent tables.

Q12. What do you mean by data integrity?

Data Integrity defines the accuracy as well as the consistency of the data stored in a database. It also
defines integrity constraints to enforce business rules on the data when it is entered into an application
or a database.

Q13. What is the difference between clustered and non-clustered index in SQL?

The differences between the clustered and non clustered index in SQL are :

1. Clustered index is used for easy retrieval of data from the database and its faster whereas
reading from non clustered index is relatively slower.
2. Clustered index alters the way records are stored in a database as it sorts out rows by the
column which is set to be clustered index whereas in a non clustered index, it does not alter the
way it was stored but it creates a separate object within a table which points back to the original
table rows after searching.

3. One table can only have one clustered index whereas it can have many non clustered index.

Q14. Write a SQL query to display the current date?

In SQL, there is a built-in function called GetDate() which helps to return the current timestamp/date.

Q15.What do you understand by query optimization?

The phase that identifies a plan for evaluation query which has the least estimated cost is known as
query optimization. The advantages of query optimization are as follows:

 The output is provided faster

 A larger number of queries can be executed in less time
 Reduces time and space complexity

Q16. What do you mean by Denormalization?

Denormalization refers to a technique which is used to access data from higher to lower forms of a
database. It helps the database managers to increase the performance of the entire infrastructure as it
introduces redundancy into a table. It adds the redundant data into a table by incorporating database
queries that combine data from various tables into a single table.

Q17. What are Entities and Relationships?

Entities: A person, place, or thing in the real world about which data can be stored in a database. Tables
store data that represents one type of entity. For example – A bank database has a customer table to
store customer information. The customer table stores this information as a set of attributes (columns
within the table) for each customer.

Relationships: Relation or links between entities that have something to do with each other. For
example – The customer name is related to the customer account number and contact information,
which might be in the same table. There can also be relationships between separate tables (for example,
customer to accounts).

Q18. What is an Index?

An index refers to a performance tuning method of allowing faster retrieval of records from the table.
An index creates an entry for each value and hence it will be faster to retrieve data.

Q19. Explain different types of index in SQL.

There are three types of index in SQL namely:

Unique Index:

This index does not allow the field to have duplicate values if the column is unique indexed. If a primary
key is defined, a unique index can be applied automatically.

Clustered Index:

This index reorders the physical order of the table and searches based on the basis of key values. Each
table can only have one clustered index.

Non-Clustered Index:

Non-Clustered Index does not alter the physical order of the table and maintains a logical order of the
data. Each table can have many non-clustered indexes.

Q20. What is Normalization and what are the advantages of it?

Normalization in SQL is the process of organizing data to avoid duplication and redundancy. Some of the
advantages are:

 Better Database organization

 More Tables with smaller rows
 Efficient data access
 Greater Flexibility for Queries
 Quickly find the information
 Easier to implement Security
 Allows easy modification
 Reduction of redundant and duplicate data
 More Compact Database
 Ensure Consistent data after modification
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Q21. What is the difference between DROP and TRUNCATE commands?

DROP command removes a table and it cannot be rolled back from the database whereas TRUNCATE
command removes all the rows from the table.

Q22. Explain different types of Normalization.

There are many successive levels of normalization. These are called normal forms. Each consecutive
normal form depends on the previous one.The first three normal forms are usually adequate.

 First Normal Form (1NF) – No repeating groups within rows

 Second Normal Form (2NF) – Every non-key (supporting) column value is dependent on the
whole primary key.
 Third Normal Form (3NF) – Dependent solely on the primary key and no other non-key
(supporting) column value.

Q23. What is the ACID property in a database?

ACID stands for Atomicity, Consistency, Isolation, Durability. It is used to ensure that the data
transactions are processed reliably in a database system.

 Atomicity: Atomicity refers to the transactions that are completely done or failed where
transaction refers to a single logical operation of a data. It means if one part of any transaction
fails, the entire transaction fails and the database state is left unchanged.
 Consistency: Consistency ensures that the data must meet all the validation rules. In simple
words, you can say that your transaction never leaves the database without completing its
state.
 Isolation: The main goal of isolation is concurrency control.
 Durability: Durability means that if a transaction has been committed, it will occur whatever
may come in between such as power loss, crash or any sort of error.

Q24. What do you mean by “Trigger” in SQL?

Trigger in SQL is are a special type of stored procedures that are defined to execute automatically in
place or after data modifications. It allows you to execute a batch of code when an insert, update or any
other query is executed against a specific table.

Q25. What are the different operators available in SQL?

There are three operators available in SQL, namely:

1. Arithmetic Operators
2. Logical Operators
3. Comparison Operators
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Q26. Are NULL values same as that of zero or a blank space?

A NULL value is not at all same as that of zero or a blank space. NULL value represents a value which is
unavailable, unknown, assigned or not applicable whereas a zero is a number and blank space is a
character.

Q27. What is the difference between cross join and natural join?

The cross join produces the cross product or Cartesian product of two tables whereas the natural join is
based on all the columns having the same name and data types in both the tables.

Q28. What is subquery in SQL?

A subquery is a query inside another query where a query is defined to retrieve data or information back
from the database. In a subquery, the outer query is called as the main query whereas the inner query is
called subquery. Subqueries are always executed first and the result of the subquery is passed on to the
main query. It can be nested inside a SELECT, UPDATE or any other query. A subquery can also use any
comparison operators such as >,< or =.

Q29. What are the different types of a subquery?

There are two types of subquery namely, Correlated and Non-Correlated.

Correlated subquery: These are queries which select the data from a table referenced in the outer
query. It is not considered as an independent query as it refers to another table and refers the column in
a table.

Non-Correlated subquery: This query is an independent query where the output of subquery is
substituted in the main query.

SQL Interview Questions

Q30. List the ways to get the count of records in a table?

To count the number of records in a table in SQL, you can use the below commands:

SELECT * FROM table1

SELECT COUNT(*) FROM table1

SELECT rows FROM sysindexes WHERE id = OBJECT_ID(table1) AND indid < 2

Q31. Write a SQL query to find the names of employees that begin with ‘A’?

To display name of the employees that begin with ‘A’, type in the below command:
1SELECT * FROM Table_name WHERE EmpName like 'A%'

Q32. Write a SQL query to get the third-highest salary of an employee from employee_table?
1SELECT TOP 1 salary

2FROM(

3SELECT TOP 3 salary

4FROM employee_table

5ORDER BY salary DESC) AS emp

6ORDER BY salary ASC;

Q33. What is the need for group functions in SQL?

Group functions work on the set of rows and return one result per group. Some of the commonly used
group functions are: AVG, COUNT, MAX, MIN, SUM, VARIANCE.

Q34 . What is a Relationship and what are they?

Relation or links are between entities that have something to do with each other. Relationships are
defined as the connection between the tables in a database. There are various relationships, namely:

 One to One Relationship.

 One to Many Relationship.
 Many to One Relationship.
 Self-Referencing Relationship.

Q35. How can you insert NULL values in a column while inserting the data?

NULL values in SQL can be inserted in the following ways:

 Implicitly by omitting column from column list.

 Explicitly by specifying NULL keyword in the VALUES clause

Q36. What is the main difference between ‘BETWEEN’ and ‘IN’ condition operators?

BETWEEN operator is used to display rows based on a range of values in a row whereas the IN condition
operator is used to check for values contained in a specific set of values.

Example of BETWEEN:
SELECT * FROM Students where ROLL_NO BETWEEN 10 AND 50;
Example of IN:

SELECT * FROM students where ROLL_NO IN (8,15,25);

Q37. Why are SQL functions used?

SQL functions are used for the following purposes:

 To perform some calculations on the data

 To modify individual data items
 To manipulate the output
 To format dates and numbers
 To convert the data types

Q38. What is the need for MERGE statement?

This statement allows conditional update or insertion of data into a table. It performs an UPDATE if a
row exists, or an INSERT if the row does not exist.

Q39. What do you mean by recursive stored procedure?

Recursive stored procedure refers to a stored procedure which calls by itself until it reaches some
boundary condition. This recursive function or procedure helps the programmers to use the same set of
code n number of times.

Q40. What is CLAUSE in SQL?

SQL clause helps to limit the result set by providing a condition to the query. A clause helps to filter the
rows from the entire set of records.

For example – WHERE, HAVING clause.

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Q41. What is the difference between ‘HAVING’ CLAUSE and a ‘WHERE’ CLAUSE?

HAVING clause can be used only with SELECT statement. It is usually used in a GROUP BY clause and
whenever GROUP BY is not used, HAVING behaves like a WHERE clause.
Having Clause is only used with the GROUP BY function in a query whereas WHERE Clause is applied to
each row before they are a part of the GROUP BY function in a query.

Q42. List the ways in which Dynamic SQL can be executed?

Following are the ways in which dynamic SQL can be executed:

 Write a query with parameters.

 Using EXEC.
 Using sp_executesql.
Q43. What are the various levels of constraints?

Constraints are the representation of a column to enforce data entity and consistency. There are two
levels of a constraint, namely:

 column level constraint

 table level constraint

Q44. How can you fetch common records from two tables?

You can fetch common records from two tables using INTERSECT. For example:

Q45. List some case manipulation functions in SQL?

There are three case manipulation functions in SQL, namely:

 LOWER: This function returns the string in lowercase. It takes a string as an argument and
returns it by converting it into lower case. Syntax:

LOWER(‘string’)

 UPPER: This function returns the string in uppercase. It takes a string as an argument and
returns it by converting it into uppercase. Syntax:

UPPER(‘string’)

 INITCAP: This function returns the string with the first letter in uppercase and rest of the letters
in lowercase. Syntax:

INITCAP(‘string’)

Q46. What are the different set operators available in SQL?

Some of the available set operators are – Union, Intersect or Minus operators.

Q47. What is an ALIAS command?

ALIAS command in SQL is the name that can be given to any table or a column. This alias name can be
referred in WHERE clause to identify a particular table or a column.

For example-

Select emp.empID, dept.Result from employee emp, department as dept where

emp.empID=dept.empID

In the above example, emp refers to alias name for employee table and dept refers to alias name for
department table.
Q48. What are aggregate and scalar functions?

Aggregate functions are used to evaluate mathematical calculation and returns a single value. These
calculations are done from the columns in a table. For example- max(),count() are calculated with
respect to numeric.

Scalar functions return a single value based on the input value. For example – UCASE(), NOW() are
calculated with respect to string.

Q49. How can you fetch alternate records from a table?

You can fetch alternate records i.e both odd and even row numbers. For example- To display even
numbers, use the following command:

Select studentId from (Select rowno, studentId from student) where mod(rowno,2)=0

Now, to display odd numbers:

Select studentId from (Select rowno, studentId from student) where mod(rowno,2)=1

Q50. Name the operator which is used in the query for pattern matching?

LIKE operator is used for pattern matching, and it can be used as -.

1. % – It matches zero or more characters.

For example- select * from students where studentname like ‘a%’

_ (Underscore) – it matches exactly one character.

For example- select * from student where studentname like ‘abc_’

Q51. How can you select unique records from a table?

You can select unique records from a table by using the DISTINCT keyword.

Select DISTINCT studentID from Student

Using this command, it will print unique student id from the table Student.

Q52. How can you fetch first 5 characters of the string?

There are a lot of ways to fetch characters from a string. For example:

Select SUBSTRING(StudentName,1,5) as studentname from student

Q53. What is the main difference between SQL and PL/SQL?

SQL is a query language that allows you to issue a single query or execute a single insert/update/delete
whereas PL/SQL is Oracle’s “Procedural Language” SQL, which allows you to write a full program (loops,
variables, etc.) to accomplish multiple operations such as selects/inserts/updates/deletes.

Q54. What is a View?

A view is a virtual table which consists of a subset of data contained in a table. Since views are not
present, it takes less space to store. View can have data of one or more tables combined and it depends
on the relationship.

Q55. What are Views used for?

A view refers to a logical snapshot based on a table or another view. It is used for the following reasons:

 Restricting access to data.

 Making complex queries simple.
 Ensuring data independence.
 Providing different views of same data.

Q56. What is a Stored Procedure?

A Stored Procedure is a function which consists of many SQL statements to access the database system.
Several SQL statements are consolidated into a stored procedure and execute them whenever and
wherever required which saves time and avoid writing code again and again.

Q57. List some advantages and disadvantages of Stored Procedure?

Advantages:

A Stored Procedure can be used as a modular programming which means create once, store and call for
several times whenever it is required. This supports faster execution. It also reduces network traffic and
provides better security to the data.

Disadvantage:

The only disadvantage of Stored Procedure is that it can be executed only in the database and utilizes
more memory in the database server.

Q58. List all the types of user-defined functions?

There are three types of user-defined functions, namely:

 Scalar Functions
 Inline Table-valued functions
 Multi-statement valued functions
Scalar returns the unit, variant defined the return clause. Other two types of defined functions return
table.

Q59. What do you mean by Collation?

Collation is defined as a set of rules that determine how data can be sorted as well as compared.
Character data is sorted using the rules that define the correct character sequence along with options
for specifying case-sensitivity, character width etc.

Q60. What are the different types of Collation Sensitivity?

Following are the different types of collation sensitivity:

 Case Sensitivity: A and a and B and b.

 Kana Sensitivity: Japanese Kana characters.
 Width Sensitivity: Single byte character and double-byte character.
 Accent Sensitivity.

Q61. What are Local and Global variables?

Local variables:

These variables can be used or exist only inside the function. These variables are not used or referred by
any other function.

Global variables:

These variables are the variables which can be accessed throughout the program. Global variables
cannot be created whenever that function is called.

Q62. What is Auto Increment in SQL?

Autoincrement keyword allows the user to create a unique number to get generated whenever a new
record_is_inserted_into_the_table.
This keyword is usually required whenever PRIMARY KEY in SQL is used.

AUTO INCREMENT keyword can be used in Oracle and IDENTITY keyword can be used in SQL SERVER.

Q63. What is a Datawarehouse?

Datawarehouse refers to a central repository of data where the data is assembled from multiple sources
of information. Those data are consolidated, transformed and made available for the mining as well as
online processing. Warehouse data also have a subset of data called Data Marts.

Q64. What are the different authentication modes in SQL Server? How can it be changed?

Windows mode and Mixed Mode – SQL and Windows. You can go to the below steps to change
authentication mode in SQL Server:
  Click Start> Programs> Microsoft SQL Server and click SQL Enterprise Manager to run SQL
Enterprise Manager from the Microsoft SQL Server program group.
 Then select the server from the Tools menu.
 Select SQL Server Configuration Properties, and choose the Security page.

Q65. What are STUFF and REPLACE function?

STUFF Function: This function is used to overwrite existing character or inserts a string into another
string. Syntax:

STUFF(string_expression,start, length, replacement_characters)

where,
string_expression: it is the string that will have characters substituted

start: This refers to the starting position

length: It refers to the number of characters in the string which are substituted.

replacement_string: They are the new characters which are injected in the string.

REPLACE function: This function is used to replace the existing characters of all the occurrences. Syntax:

REPLACE (string_expression, search_string, replacement_string)

DATA Modeling

1. What Are the Three Types of Data Models?

The three types of data models:

 Physical data model - This is where the framework or schema describes how data is physically
stored in the database.
 Conceptual data model - This model focuses on the high-level, user’s view of the data in
question
 Logical data models - They straddle between physical and theoretical data models, allowing the
logical representation of data to exist apart from the physical storage.

2. What is a Table?

A table consists of data stored in rows and columns. Columns, also known as fields, show data in vertical
alignment. Rows also called a record or tuple, represent data’s horizontal alignment.

3. What is Normalization?

Database normalization is the process of designing the database in such a way that it reduces data
redundancy without sacrificing integrity.
4. What Does a Data Modeler Use Normalization For?

The purposes of normalization are:

 Remove useless or redundant data

 Reduce data complexity
 Ensure relationships between the tables in addition to the data residing in the tables
 Ensure data dependencies and that the data is stored logically.

5. So, What is Denormalization, and What is its Purpose?

Denormalization is a technique where redundant data is added to an already normalized database. The
procedure enhances read performance by sacrificing write performance.

6. What Does ERD Stand for, and What is it?

ERD stands for Entity Relationship Diagram and is a logical entity representation, defining the
relationships between the entities. Entities reside in boxes, and arrows symbolize relationships.

7. What’s the Definition of a Surrogate Key?

A surrogate key, also known as a primary key, enforces numerical attributes. This surrogate key replaces
natural keys. Instead of having primary or composite primary keys, data modelers create the surrogate
key, which is a valuable tool for identifying records, building SQL queries, and enhancing performance.

8. What Are the Critical Relationship Types Found in a Data Model? Describe Them.

The main relationship types are:

 Identifying. A relationship line normally connects parent and child tables. But if a child table’s
reference column is part of the table’s primary key, the tables are connected by a thick line,
signifying an identifying relationship.
 Non-identifying. If a child table’s reference column is NOT a part of the table’s primary key, the
tables are connected by a dotted line, signifying a no-identifying relationship.
 Self-recursive. A recursive relationship is a standalone column in a table connected to the
primary key in the same table.

9. What is an Enterprise Data Model?

This is a data model that consists of all the entries required by an enterprise.

Intermediate Data Modeling Interview Questions

10. What Are the Most Common Errors You Can Potentially Face in Data Modeling?

These are the errors most likely encountered during data modeling.
  Building overly broad data models: If tables are run higher than 200, the data model becomes
increasingly complex, increasing the likelihood of failure
 Unnecessary surrogate keys: Surrogate keys must only be used when the natural key cannot
fulfill the role of a primary key
 The purpose is missing: Situations may arise where the user has no clue about the business’s
mission or goal. It’s difficult, if not impossible, to create a specific business model if the data
modeler doesn’t have a workable understanding of the company’s business model
 Inappropriate denormalization: Users shouldn’t use this tactic unless there is an excellent reason
to do so. Denormalization improves read performance, but it creates redundant data, which is a
challenge to maintain.

11. Explain the Two Different Design Schemas.

The two design schema is called Star schema and Snowflake schema. The Star schema has a fact table
centered with multiple dimension tables surrounding it. A Snowflake schema is similar, except that the
level of normalization is higher, which results in the schema looking like a snowflake.

12. What is a Slowly Changing Dimension?

These are dimensions used to manage both historical data and current data in data-warehousing. There
are four different types of slowly changing dimensions: SCD Type 0 through SCD Type 3.

13. What is Data Mart?

A data mart is the most straightforward set of data warehousing and is used to focus on one functional
area of any given business. Data marts are a subset of data warehouses oriented to a specific line of
business or functional area of an organization (e.g., marketing, finance, sales). Data enters data marts by
an assortment of transactional systems, other data warehouses, or even external sources.

14. What is Granularity?

Granularity represents the level of information stored in a table. Granularity is defined as high or low.
High granularity data contains transaction-level data. Low granularity has low-level information only,
such as that found in fact tables.

15. What is Data Sparsity, and How Does it Impact Aggregation?

Data sparsity defines how much data we have for a model’s specified dimension or entity. If there is
insufficient information stored in the dimensions, then more space is needed to store these
aggregations, resulting in an oversized, cumbersome database.

16. What Are Subtype and Supertype Entities?

Entities can be broken down into several sub-entities or grouped by specific features. Each sub-entity
has relevant attributes and is called a subtype entity. Attributes common to every entity are placed in a
higher or super level entity, which is why they are called supertype entities.
17. In the Context of Data Modeling, What is the Importance of Metadata?

Metadata is defined as “data about data.” In the context of data modeling, it’s the data that covers what
types of data are in the system, what it’s used for, and who uses it.

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Advanced-Data Modeling Interview Questions

18. Should All Databases Be Rendered in 3NF?

No, it’s not an absolute requirement. However, denormalized databases are easily accessible, easier to
maintain, and less redundant.

19. What’s the Difference Between forwarding and Reverse Engineering, in the Context of Data Models?

Forward engineering is a process where Data Definition Language (DDL) scripts are generated from the
data model itself. DDL scripts can be used to create databases. Reverse Engineering creates data models
from a database or scripts. Some data modeling tools have options that connect with the database,
allowing the user to engineer a database into a data model.

20. What Are Recursive Relationships, and How Do You Rectify Them?

Recursive relationships happen when a relationship exists between an entity and itself. For instance, a
doctor could be in a health center’s database as a care provider, but if the doctor is sick and goes in as a
patient, this results in a recursive relationship. You would need to add a foreign key to the health
center’s number in each patient’s record.

21. What’s a Confirmed Dimension?

If a dimension is confirmed, it’s attached to at least two fact tables.

22. Why Are NoSQL Databases More Useful than Relational Databases?

NoSQL databases have the following advantages:

 They can store structured, semi-structured, or unstructured data

 They have a dynamic schema, which means they can evolve and change as quickly as needed
 NoSQL databases have sharding, the process of splitting up and distributing data to smaller
databases for faster access
 They offer failover and better recovery options thanks to the replication
 It’s easily scalable, growing or shrinking as necessary
23. What’s a Junk Dimension?

This is a grouping of low-cardinality attributes like indicators and flags, removed from other tables, and
subsequently “junked” into an abstract dimension table. They are often used to initiate Rapidly
Changing Dimensions within data warehouses.

24. If a Unique Constraint Gets Applied to a Column, Will It Generate an Error If You Attempt to Place
Two Nulls in It?

No, it won’t, because null error values are never equal. You can put in numerous null values in a column
and not generate an error.