SQL Tutorial - UPDATE Query

An UPDATE statement in SQL can be used to update existing records in a table.
You can either update a single record, or multiple records in a table.
You can specify which records to update via a WHERE clause.
Syntax of UPDATE Statement is as follows:

UPDATE TABLENAME SET column1=value1, column2=value2... columnN=valueN
	   WHERE condition

Imagine we have table called CUSTOMER, with the following data:

Rambo

Robert

Belgium

Mugambo

Norway

Nagashekar

Rao

India

Scenario 1: Update a record in Customer table. Add a Last name to Mugambo. Lastname: Kichidi
We can use an UPDATE statement as follows.

UPDATE CUSTOMER SET LASTNAME='Kichidi' WHERE FIRSTNAME='Mugambo'

Result: 1 Row updated. Table contents:

Rambo

Robert

Belgium

Mugambo

Kichidi

Norway

Nagashekar

Rao

India

In the above UPDATE statement, we set the lastname to Kichidi when the first name is Mugambo.

Scenario 2: Update Customers from Belgium and Norway such that their age is 22
We can use a UPDATE statement as follows.

UPDATE CUSTOMER SET AGE=22 WHERE COUNTRY IN ('Belgium', 'Norway')

Result: 2 Rows updated. Table contents:

Rambo

Robert

Belgium

Mugambo

Kichidi

Norway

Nagashekar

Rao

India

In the above UPDATE statement, we set the AGE to 22 when the COUNTRY is either BELGIUM or NORWAY.

Note: if you want to update all the records in a TABLE, you can either exclude the WHERE clause or use WHERE 1=1.