MANIPULATING DATA

OBJECTIVES
 After completing this lesson, you should be able to do
the following:
 Describe each data manipulation language (DML) statement
 Insert rows into a table
 Update rows in a table
 Delete rows from a table
 Control transactions
LESSON AGENDA
 Adding new rows in a table
 INSERT statement
 Changing data in a table
 UPDATE statement
 Removing rows from a table:
 DELETE statement
 TRUNCATE statement

 Databasetransactions control using COMMIT, ROLLBACK, and

SAVEPOINT
 Read consistency
 FOR UPDATE clause in a SELECT statement
DATA MANIPULATION LANGUAGE
 A DML statement is executed when you:
 Add new rows to a table
 Modify existing rows in a table

 Remove existing rows from a table

 A transaction consists of a collection of DML statements that

form a logical unit of work.
ADDING A NEW ROW TO A TABLE
New
DEPARTMENTS row

Insert new row

into the
DEPARTMENTS table.
INSERT STATEMENT SYNTAX
 Add new rows to a table by using the INSERT statement:

INSERT INTO table [(column [, column...])]

VALUES (value [, value...]);

 With this syntax, only one row is inserted at a time.

INSERTING NEW ROWS
 Inserta new row containing values for each column.
 List values in the default order of the columns in the table.
 Optionally, list the columns in the INSERT clause.

INSERT INTO departments(department_id,

department_name, manager_id, location_id)
VALUES (70, 'Public Relations', 100, 1700);
 Enclose character and date values within single quotation marks.
INSERTING ROWS WITH NULL VALUES
 Implicitmethod: Omit the column from the
column list.
INSERT INTO departments (department_id,
department_name)
VALUES (30, 'Purchasing');

 Explicit method: Specify the NULL keyword in the VALUES

clause.

INSERT INTO departments

VALUES (100, 'Finance', NULL, NULL);
INSERTING SPECIAL VALUES
 The SYSDATE function records the current date and time.
INSERT INTO employees (employee_id,
first_name, last_name,
email, phone_number,
hire_date, job_id, salary,
commission_pct, manager_id,
department_id)
VALUES (113,
'Louis', 'Popp',
'LPOPP', '515.124.4567',
SYSDATE, 'AC_ACCOUNT', 6900,
NULL, 205, 110);
INSERTING SPECIFIC DATE AND TIME
VALUES
 Add a new employee.
INSERT INTO employees
VALUES (114,
'Den', 'Raphealy',
'DRAPHEAL', '515.127.4561',
TO_DATE('FEB 3, 1999', 'MON DD, YYYY'),
'SA_REP', 11000, 0.2, 100, 60);

 Verify your addition.

CREATING A SCRIPT
 Use & substitution in a SQL statement to prompt for values.
 & is a placeholder for the variable value.

INSERT INTO departments

(department_id, department_name, location_id)
VALUES (&department_id, '&department_name',&location);
COPYING ROWS
FROM ANOTHER TABLE
 Write your INSERT statement with a subquery:
INSERT INTO sales_reps(id, name, salary, commission_pct)
SELECT employee_id, last_name, salary, commission_pct
FROM employees
WHERE job_id LIKE '%REP%';

 Do not use the VALUES clause.

 Match the number of columns in the INSERT clause to those in
the subquery.
 Inserts all the rows returned by the subquery in the table,
sales_reps.
LESSON AGENDA
 Adding new rows in a table
 INSERT statement
 Changing data in a table
 UPDATE statement
 Removing rows from a table:
 DELETE statement
 TRUNCATE statement

 Databasetransactions control using COMMIT, ROLLBACK, and

SAVEPOINT
 Read consistency
 FOR UPDATE clause in a SELECT statement
CHANGING DATA IN A TABLE
EMPLOYEES

Update rows in the EMPLOYEES table:

UPDATE STATEMENT SYNTAX
 Modify existing values in a table with the UPDATE statement:
UPDATE table
SET column = value [, column = value, ...]
[WHERE condition];
 Update more than one row at a time (if required).
UPDATING ROWS IN A TABLE
 Values
for a specific row or rows are modified if you specify the
WHERE clause:

UPDATE employees
SET department_id = 50
WHERE employee_id = 113;

 Values
for all the rows in the table are modified if you omit the
WHERE clause:

UPDATE copy_emp
SET department_id = 110;

 Specify SET column_name= NULL to update a column value to

NULL.
UPDATING TWO COLUMNS WITH A
SUBQUERY
 Update employee 113’s job and salary to match those of employee
205.

UPDATE employees
SET job_id = (SELECT job_id
FROM employees
WHERE employee_id = 205),
salary = (SELECT salary
FROM employees
WHERE employee_id = 205)
WHERE employee_id = 113;
UPDATING ROWS BASED
ON ANOTHER TABLE
 Use the subqueries in the UPDATE statements to update row values in a
table based on values from another table:

UPDATE copy_emp
SET department_id = (SELECT department_id
FROM employees
WHERE employee_id = 100)
WHERE job_id = (SELECT job_id
FROM employees
WHERE employee_id = 200);
LESSON AGENDA
 Adding new rows in a table
 INSERT statement
 Changing data in a table
 UPDATE statement
 Removing rows from a table:
 DELETE statement
 TRUNCATE statement

 Databasetransactions control using COMMIT, ROLLBACK, and

SAVEPOINT
 Read consistency
 FOR UPDATE clause in a SELECT statement
REMOVING A ROW FROM A TABLE
DEPARTMENTS

Delete a row from the DEPARTMENTS table:

DELETE STATEMENT
 You can remove existing rows from a table by using the DELETE
statement:

DELETE [FROM] table

[WHERE condition];
DELETING ROWS FROM A TABLE
 Specific rows are deleted if you specify the WHERE clause:

DELETE FROM departments

WHERE department_name = ‘Finance';

 All rows in the table are deleted if you omit the WHERE clause:

DELETE FROM copy_emp;

DELETING ROWS BASED
ON ANOTHER TABLE
 Use the subqueries in the DELETE statements to remove rows from a table
based on values from another table:

DELETE FROM employees

WHERE department_id =
(SELECT department_id
FROM departments
WHERE department_name
LIKE '%Public%');
TRUNCATE STATEMENT
 Removes all rows from a table, leaving the table empty and the
table structure intact
 Is a data definition language (DDL) statement rather than a DML
statement; cannot easily be undone
 Syntax:

TRUNCATE TABLE table_name;

 Example:

TRUNCATE TABLE copy_emp;

LESSON AGENDA
 Adding new rows in a table
 INSERT statement
 Changing data in a table
 UPDATE statement
 Removing rows from a table:
 DELETE statement
 TRUNCATE statement

 Databasetransactions control using COMMIT, ROLLBACK, and

SAVEPOINT
 Read consistency
 FOR UPDATE clause in a SELECT statement
DATABASE TRANSACTIONS
 A database transaction consists of one of the following:
 DML statements that constitute one consistent change to
the data
 One DDL statement
 One data control language (DCL) statement
DATABASE TRANSACTIONS: START AND
END
 Beginwhen the first DML SQL statement is executed.
 End with one of the following events:
 A COMMIT or ROLLBACK statement is issued.
 A DDL or DCL statement executes (automatic commit).

 The user exits SQL Developer or SQL*Plus.

 The system crashes.

ADVANTAGES OF COMMIT
AND ROLLBACK STATEMENTS
 With COMMIT and ROLLBACK statements, you can:
 Ensure data consistency
 Preview data changes before making changes permanent
 Group logically-related operations
EXPLICIT TRANSACTION CONTROL
STATEMENTS
Time COMMIT
Transaction

DELETE

SAVEPOINT A

INSERT

UPDATE

SAVEPOINT B

INSERT
ROLLBACK ROLLBACK ROLLBACK
to SAVEPOINT B to SAVEPOINT A
ROLLING BACK CHANGES TO A
MARKER
 Create a marker in the current transaction by using the
SAVEPOINT statement.
 Roll back to that marker by using the ROLLBACK TO
SAVEPOINT statement.

UPDATE...
SAVEPOINT update_done;

INSERT...
ROLLBACK TO update_done;
IMPLICIT TRANSACTION PROCESSING
 An automatic commit occurs in the following circumstances:
 A DDL statement is issued
 A DCL statement is issued

 Normal exit from SQL Developer or SQL*Plus, without explicitly issuing

COMMIT or ROLLBACK statements

 An automatic rollback occurs when there is an abnormal
termination of SQL Developer or SQL*Plus or a system failure.
STATE OF THE DATA
BEFORE COMMIT OR ROLLBACK
 The previous state of the data can be recovered.
 The current user can review the results of the DML operations by
using the SELECT statement.
 Other users cannot view the results of the DML statements issued
by the current user.
 The affected rows are locked; other users cannot change the data
in the affected rows.
STATE OF THE DATA AFTER COMMIT
 Data changes are saved in the database.
 The previous state of the data is overwritten.
 All users can view the results.
 Locks on the affected rows are released; those rows are available
for other users to manipulate.
 All savepoints are erased.
COMMITTING DATA
 Make the changes:
DELETE FROM employees
WHERE employee_id = 99999;

INSERT INTO departments

VALUES (290, 'Corporate Tax', NULL, 1700);

 Commit the changes:

COMMIT;
STATE OF THE DATA AFTER ROLLBACK
 Discard all pending changes by using the ROLLBACK
statement:
 Data changes are undone.
 Previous state of the data is restored.
 Locks on the affected rows are released.

DELETE FROM copy_emp;

ROLLBACK ;
STATE OF THE DATA AFTER ROLLBACK:
EXAMPLE

DELETE FROM test;

25,000 rows deleted.

ROLLBACK;
Rollback complete.

DELETE FROM test WHERE id = 100;

1 row deleted.

SELECT * FROM test WHERE id = 100;

No rows selected.

COMMIT;
Commit complete.
STATEMENT-LEVEL ROLLBACK
 If a single DML statement fails during execution, only that
statement is rolled back.
 The Oracle server implements an implicit savepoint.
 All other changes are retained.
 The user should terminate transactions explicitly by executing a
COMMIT or ROLLBACK statement.
LESSON AGENDA
 Adding new rows in a table
 INSERT statement
 Changing data in a table
 UPDATE statement
 Removing rows from a table:
 DELETE statement
 TRUNCATE statement

 Databasetransactions control using COMMIT, ROLLBACK, and

SAVEPOINT
 Read consistency
 FOR UPDATE clause in a SELECT statement
READ CONSISTENCY
 Read consistency guarantees a consistent view of the data at all
times.
 Changes made by one user do not conflict with the changes made
by another user.
 Read consistency ensures that, on the same data:
 Readers do not wait for writers
 Writers do not wait for readers

 Writers wait for writers

IMPLEMENTING READ CONSISTENCY
User A

UPDATE employees Data

SET salary = 7000 blocks
WHERE last_name = 'Grant';

Undo
segments

Changed
SELECT * and
FROM userA.employees; Read- unchanged
consistent data
image Before
change
User B (“old” data)
LESSON AGENDA
 Adding new rows in a table
 INSERT statement
 Changing data in a table
 UPDATE statement
 Removing rows from a table:
 DELETE statement
 TRUNCATE statement

 Databasetransactions control using COMMIT, ROLLBACK, and

SAVEPOINT
 Read consistency
 FOR UPDATE clause in a SELECT statement
FOR UPDATE CLAUSE IN A SELECT
STATEMENT
 Locksthe rows in the EMPLOYEES table where job_id is
SA_REP.
SELECT employee_id, salary, commission_pct, job_id
FROM employees
WHERE job_id = 'SA_REP'
FOR UPDATE
ORDER BY employee_id;

 Lock is released only when you issue a ROLLBACK or a

COMMIT.
 If the SELECT statement attempts to lock a row that is locked by
another user, then the database waits until the row is available,
and then returns the results of the SELECT statement.
FOR UPDATE CLAUSE: EXAMPLES
 You can use the FOR UPDATE clause in a SELECT statement
against multiple tables.

SELECT e.employee_id, e.salary, e.commission_pct

FROM employees e JOIN departments d
USING (department_id)
WHERE job_id = 'ST_CLERK‘
AND location_id = 1500
FOR UPDATE
ORDER BY e.employee_id;
 Rows from both the EMPLOYEES and DEPARTMENTS tables are
locked.
 Use FOR UPDATE OF column_name to qualify the column you
intend to change, then only the rows from that specific table are
locked.
SUMMARY
 In this lesson, you should have learned how to use the following
statements:

Function Description
INSERT Adds a new row to the table
UPDATE Modifies existing rows in the table
DELETE Removes existing rows from the table
TRUNCATE Removes all rows from a table
COMMIT Makes all pending changes permanent
SAVEPOINT Is used to roll back to the savepoint marker
ROLLBACK Discards all pending data changes
FOR UPDATE clause Locks rows identified by the SELECT query
in SELECT
PRACTICE 9: OVERVIEW
 This practice covers the following topics:
 Insertingrows into the tables
 Updating and deleting rows in the table
 Controlling transactions