UPDATE

The SQL UPDATE Statement is used to modify the existing rows in a table.

Syntax:

Basic syntax of UPDATE statement is as follows:

UPDATE table_name

SET column1 = value1, column2 = value2...., columnN = valueN

WHERE [condition];

You can combine N number of conditions.

      table_name -  the table name which has to be updated.

column_name1, column_name2.. - the columns that gets changed.

 value1, value2... - are the new values.

NP: You can use WHERE clause with UPDATE query to update selected rows. If you do not include the WHERE clause, column values for all the rows get affected.

EXAMPLE:

Below is the "EMPLOYEE1" table:

ID	NAME	START_DATE	END_DATE	SALARY	CITY
1	A	01/01/2016 00:00:00	01/06/2016 00:00:00	10,000	CHENNAI
2	B	02/01/2016 00:00:00	07/03/2016 00:00:00	10,000	BOMBAY
3	C	03/01/2016 00:00:00	08/06/2016 00:00:00	10,000	DELHI
4	D	01/01/2016 00:00:00	07/06/2016 00:00:00	10,000	PUNE
5	E	01/01/2016 00:00:00	09/06/2016 00:00:00	10,000	NOIDA
6	F	01/01/2016 00:00:00	08/06/2016 00:00:00	10,000	BHUBANESWAR
7	G	01/01/2016 00:00:00	07/06/2016 00:00:00	10,000	HYDERABAD
8	H	01/01/2016 00:00:00	06/06/2016 00:00:00	10,000	KOLKATA

1)To update the name and city of an employee in EMPLOYEE1 table whose ID = 8, the SQL update query would be like,

UPDATE EMPLOYEE1

SET NAME = ‘Z’, CITY = ‘NOIDA’

WHERE ID = 8;

ID	NAME	START_DATE	END_DATE	SALARY	CITY
1	A	01/01/2016 00:00:00	01/06/2016 00:00:00	10,000	CHENNAI
2	B	02/01/2016 00:00:00	07/03/2016 00:00:00	10,000	BOMBAY
3	C	03/01/2016 00:00:00	08/06/2016 00:00:00	10,000	DELHI
4	D	01/01/2016 00:00:00	07/06/2016 00:00:00	10,000	PUNE
5	E	01/01/2016 00:00:00	09/06/2016 00:00:00	10,000	NOIDA
6	F	01/01/2016 00:00:00	08/06/2016 00:00:00	10,000	BHUBANESWAR
7	G	01/01/2016 00:00:00	07/06/2016 00:00:00	10,000	HYDERABAD
8	Z	01/01/2016 00:00:00	06/06/2016 00:00:00	10,000	NOIDA

2)To update the city of all the employees, the query would be,

UPDATE EMPLOYEE1

SET CITY = 'Pune';

ID	NAME	START_DATE	END_DATE	SALARY	CITY
1	A	01/01/2016 00:00:00	01/06/2016 00:00:00	10,000	Pune
2	B	02/01/2016 00:00:00	07/03/2016 00:00:00	10,000	Pune
3	C	03/01/2016 00:00:00	08/06/2016 00:00:00	10,000	Pune
4	D	01/01/2016 00:00:00	07/06/2016 00:00:00	10,000	Pune
5	E	01/01/2016 00:00:00	09/06/2016 00:00:00	10,000	Pune
6	F	01/01/2016 00:00:00	08/06/2016 00:00:00	10,000	Pune
7	G	01/01/2016 00:00:00	07/06/2016 00:00:00	10,000	Pune
8	Z	01/01/2016 00:00:00	06/06/2016 00:00:00	10,000	Pune