SQL UPDATE

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

SQL UPDATE Syntax

UPDATE table_name SET column1=value, column2=value2,... WHERE some_column=some_value

Note: Notice the WHERE clause in the UPDATE syntax. The WHERE clause specifies which record or records that should be updated. If you omit the WHERE clause, all records will be updated!

SQL UPDATE Example

The "Persons" table:

Id	LastName	FirstName	Address	City
1	Navis	Anto	Madras	TVL
2	Ji	Bala	Bombay	TVL
3	Christopher	Franklin	America	KK
4	Nilsen	Johan	Bakken 2	KK
5	Tjessem	Jakob

Now we want to update the person "Tjessem, Jakob" in the "Persons" table.

We use the following SQL statement:

UPDATE Persons SET Address='Nissestien 67', City='TVL' WHERE LastName='Tjessem' AND FirstName='Jakob'

The "Persons" table will now look like this:

Id	LastName	FirstName	Address	City
1	Navis	Anto	Madras	TVL
2	Ji	Bala	Bombay	TVL
3	Christopher	Franklin	America	KK
4	Nilsen	Johan	Bakken 2	KK
5	Tjessem	Jakob	Nissestien 67	TVL

SQL UPDATE Warning

Be careful when updating records. If we had omitted the WHERE clause in the example above, like this:

UPDATE Persons SET Address='Nissestien 67', City='TVL'

The "Persons" table would have looked like this:

Id	LastName	FirstName	Address	City
1	Navis	Anto	Nissestien 67	TVL
2	Ji	Bala	Nissestien 67	TVL
3	Christopher	Franklin	Nissestien 67	TVL
4	Nilsen	Johan	Nissestien 67	TVL
5	Tjessem	Jakob	Nissestien 67	TVL