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DDL - Data Definition Language

A data definition language (DDL) is used to define and modify database objects like tables, views, and schemas. It describes the structure of database tables by defining columns and specifying column data types. Common DDL commands include CREATE, ALTER, RENAME, DROP, and TRUNCATE. The document provides examples of using DDL commands like CREATE TABLE and ALTER TABLE to define a table structure and modify it. It also describes data types that can be used for columns and provides a sample query to create a table for employees with columns for ID, name, and contact number.

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192 views9 pages

DDL - Data Definition Language

A data definition language (DDL) is used to define and modify database objects like tables, views, and schemas. It describes the structure of database tables by defining columns and specifying column data types. Common DDL commands include CREATE, ALTER, RENAME, DROP, and TRUNCATE. The document provides examples of using DDL commands like CREATE TABLE and ALTER TABLE to define a table structure and modify it. It also describes data types that can be used for columns and provides a sample query to create a table for employees with columns for ID, name, and contact number.

Uploaded by

Arun Kumar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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DDL – Data Definition Language

A data definition language (DDL) is a computer language used to


create and modify the structure of database objects in a database.
These database objects include views, schemas, tables, indexes, etc.

This term is also known as data description language in some


contexts, as it describes the fields and records in a database table.
The DDL used in the SQL queries are
• Create
• Alter (Rename, Add, Modify, Drop)
• Rename
• Drop
• Truncate
Syntax for creating table:
CREATE TABLE table_name
(
Columnname datatype n()
) ;
Types of data type :
• Char()
• Int()
• Long
• Varchar()
• Varchar2()
• Date
• Float()
• Raw()
• Long raw
Each Column name should have its appropriate data type according to
the value to be entered.
Query: Create a table for a batch of employees

Create table tab_emp21


(
Emp_id varchar(5),
Emp_name Char(10),
Emp_cont number(10)
) ;

Query result:

Alter:
ALTER TABLE statement is used to add, delete, rename, drop and
modify the column in the table.
Syntax for adding a column:
AFTER TABLE table_name
Add column_name datatype ();
Query:
Add a new column Emp_sal in the existing table.

ALTER TABLE tab_emp21


Add Emp_sal number(10);

Result:

Syntax for Modifying table:


To modify the datatype.
ALTER TABLE tablename
Modify column_name newdatatype();

Query:
Modify thw Emp_sal from number() to varchar2()
ALTER TABLE tab_emp21
Modify Emp_id varchar2(10);
Result:

Rename a column name:


ALTER TABLE tablename
RENAME COLUMN old name TO new name

Query:
Rename column Emp_cont to Emp_ph
ALTER TABLE tab_ emp21
RENAME COLUMN Emp_cont TO Emp_ph
Result:

Dropping a column:

ALTER TABLE table_name


DROP COLUMN column name;
Query:
Drop Emp_mail
ALTER TABLE tab_batch DROP
COLUMN Emp_mail;
Result:

Renaming the table:


Syntax:
RENAME old table_name to new table_name;

Query: Change the old table name RENAME


tab_emp21 TO tb_emp;
Result:

Truncate: Clears all the data in the database table Syntax:


TRUNCATE TABLE table_name;

Drop: Deletes the entire table itself Syntax:


DROP TABLE table_name;

DML- DATA MANIPULATING LANGUAGE


This is used to insert, update, delete and merge data in the database
table.
Insert value in table Method
1:
Syntax:
INSERT INTO table_name(column name1, column name2, column
name n)
VALUES (v1, v2, vn);
Query:
To insert values for the tb_emp.
INSERT INTO tb_batch(Emp_id,Emp_name,Emp_ph,Emp_sal)
VALUES (‘OM1001’, ‘Arun’, ‘94879’, ‘50,000’);
Result:

Method 2:
Syntax:
INSERT INTO table_name Values (v1,v2,vn);

Update:
Used to enter new value

Syntax:
UPDATE table_name
SET column name = New value
WHERE condition;
QUERY:
INSERT INTO tb_emp (Emp_id,Emp_name,Emp_sal)
VALUES ('102','Neil','10000');

UPDATE tb_emp
Emp_ph='989898989
SET
8'
WHERE Emp_id='102';

SELECT *
FROM tb_emp;
Result:
Delete:
To delete particular data.
Syntax:
DELETE FROM table_name;
WHERE condition;

Query:
DELETE FROM tb_emp WHERE
emp_name='Adam';
Result:

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