SQL UPDATE

The SQL UPDATE Statement

The UPDATE statement is employed to alter existing records within a table.

UPDATE Syntax

UPDATE table_name

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

 WHERE condition;

Note: Caution should be exercised when updating records in a table. Pay attention to the WHERE clause in the UPDATE statement, which specifies which record(s) should be updated. Omitting the WHERE clause will result in all records in the table being updated.

Demo Database

Here is an excerpt from the Customers table that has been referenced in the examples:

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 subsequent 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;

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

The number of records to be updated is determined by the WHERE clause.

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

Example

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

Here is how the selection from the “Customers” table will appear now:

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!

Exercise caution when updating records. If you omit the WHERE clause, you will update ALL records!

Example

UPDATE Customers
SET ContactName=‘Juan’;

The excerpt from the “Customers” table will now appear as follows:

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