SQL Update

Guides • SQL • 15/04/2021

The SQL UPDATE Statement

The UPDATE statement is used to modify the existing records in a table.

UPDATE Syntax

SQL

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition; 

Important:
Be careful when updating records in a table! Notice the WHERE clause in the UPDATE statement. The WHERE clause specifies which record(s) that should be updated. If you omit the WHERE clause, all records in the table will be updated!

UPDATE Table

The following SQL statement updates the first customer (CustomerID = 1) with a new contact person and a new city.

SQL

UPDATE Customers
SET ContactName = 'Alfred Schmidt', City= 'Frankfurt'
WHERE CustomerID = 1;

UPDATE Multiple Records

It is the WHERE clause that determines how many records will be updated.

The following SQL statement will update the ContactName to “Juan” for all records where country is “Mexico”:

SQL

UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';

UPDATE Warning

Important:
Be careful when updating records. If you omit the WHERE clause, ALL records will be updated!

SQL

UPDATE Customers
SET ContactName='Juan';

This will update the ContactName fields in ALL records to ‘Juan’!