SQL UPDATE Statement

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

“Persons” TABLE:

P_Id	LastName	FirstName	Address	City
1	Suhail	Osmani	Maharaj Nagar	Sitapur
2	Maxwel	Tom	Biswan	Sitapur
3	Rahi	Ayon	Okhla	Delhi
4	Nyla	Johan	Bakken 2	Delhi
5	Thoria	Jakob

Now we want to update the person "Thoria, Jakob" in “Persons” TABLE.
We use the following SQL statement:

UPDATE Persons SET Address='New Road', City='Sitapur' WHERE LastName='Thoria' AND FirstName='Jakob'

“Persons” TABLE will now look like this:

P_Id	LastName	FirstName	Address	City
1	Suhail	Osmani	Maharaj Nagar	Sitapur
2	Maxwel	Tom	Biswan	Sitapur
3	Rahi	Ayon	Okhla	Delhi
4	Nyla	Johan	Bakken 2	Delhi
5	Thoria	Jakob	New Road	Sitapur

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='New Road', City='Sitapur'

“Persons” TABLE would have looked like this:

P_Id	LastName	FirstName	Address	City
1	Suhail	Osmani	New Road	Sitapur
2	Maxwel	Tom	New Road	Sitapur
3	Rahi	Ayon	New Road	Sitapur
4	Nyla	Johan	New Road	Sitapur
5	Thoria	Jakob	New Road	Sitapur