SQL UPDATE Statement

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

UPDATE Syntax

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

Note:

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!

 

Demo Database

Below is a selection from the “Customers” table in the Northwind sample database:

CustomerID CustomerName ContactName Address City PostalCode Country
1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany
2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

 

UPDATE Table

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

Example

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

Output

The selection from the “Customers” table will now look like this:

CustomerID CustomerName ContactName Address City PostalCode Country
1 Alfreds Futterkiste Alfred Schmidt Obere Str. 57 Frankfurt 12209 Germany
2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

 

UPDATE Multiple Records

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

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

Example

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

output

The selection from the “Customers” table will now look like this:

CustomerID CustomerName ContactName Address City PostalCode Country
1 Alfreds Futterkiste Alfred Schmidt Obere Str. 57 Frankfurt 12209 Germany
2 Ana Trujillo Emparedados y helados Juan Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Juan Mataderos 2312 México D.F. 05023 Mexico
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

 

Update Warning!

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

Example

UPDATE Customers
SET ContactName=’Juan’;

output

The selection from the “Customers” table will now look like this:

CustomerID CustomerName ContactName Address City PostalCode Country
1 Alfreds Futterkiste Juan Obere Str. 57 Frankfurt 12209 Germany
2 Ana Trujillo Emparedados y helados Juan Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Juan Mataderos 2312 México D.F. 05023 Mexico
4 Around the Horn Juan 120 Hanover Sq. London WA1 1DP UK
5 Berglunds snabbköp Juan Berguvsvägen 8 Luleå S-958 22 Sweden