DML: UPDATE

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

Basic Syntax

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

• table_name: The table to update.
• column1 = value1, column2 = value2, …: The column(s) to update and the new value(s).
• condition: An optional clause to filter rows to update.

It’s very important to always use the WHERE clause in an UPDATE statement. Without it, all records will be updated.

Example 1 - Basic UPDATE

For the “customer” table:

If we want to update Sally’s country to Canada, we can use the following SQL:

UPDATE customer
SET country = 'Canada'
WHERE name = 'Sally';

The “customer” table would now look like this:

Example 2 - Update Multiple Columns

If we want to update both Sally’s name and country to Sam and Australia, we can use the following SQL:

UPDATE customer
SET name = 'Sam', country = 'Australia'
WHERE customer_id = 4;

The “customer” table would now look like this:

Example 3 - Update All Rows

If we want to update all rows in a column, we can do so without the WHERE clause. However, be careful because this will change all rows in the specified column(s).

UPDATE product
SET price = price * 1.1;

This will increase the price of all products by 10%.

1. SQL UPDATE Statement - W3Schools
2. The SQL UPDATE Statement - SQL Tutorial
3. Update Data In a MySQL Table Using MySQLi and PDO - W3Schools
4. SQL Server UPDATE Statement - SQL Server Tutorial
5. UPDATE (Transact-SQL) - Microsoft Docs