SQL UPDATE Statement

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

The UPDATE Statement

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:

P_Id	LastName	FirstName	Address	City
1	Karmen	Kasa	Los Angels - USA	New Orleans
2	Jacob	Mary	Los Angels - USA	New Orleans
3	Maxwell	Glen	Australia	Sydney
4	Tendulkar	Sachin	India MH	Mumbai
5	Laxmi	Mary

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

We use the following SQL statement:

UPDATE Persons
SET Address='India TN', City='Tamilnadu'
WHERE LastName='Nehwal' AND FirstName='Jakob'

The "Persons" table will now look like this:

P_Id	LastName	FirstName	Address	City
1	Karmen	Kasa	Los Angels - USA	New Orleans
2	Jacob	Mary	Los Angels - USA	New Orleans
3	Maxwell	Glen	Australia	Sydney
4	Tendulkar	Sachin	India MH	Mumbai
5	Laxmi	Mary	India TN	Tamilnadu

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='India TN', City='New Orleans'

The "Persons" table would have looked like this:

P_Id	LastName	FirstName	Address	City
1	Karmen	Kasa	India TN	Tamilnadu
2	Jacob	Mary	India TN	Tamilnadu
3	Maxwell	Glen	India TN	Tamilnadu
4	Tendulkar	Sachin	India TN	Tamilnadu
5	Laxmi	Mary	India TN	Tamilnadu

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