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
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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 |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
| 2 |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
| 3 |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
| 4 |
Nilsen |
Johan |
Bakken 2 |
Stavanger |
| 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='Sandnes'
WHERE LastName='Tjessem' AND FirstName='Jakob'
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The "Persons" table will now look like this:
| P_Id |
LastName |
FirstName |
Address |
City |
| 1 |
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
| 2 |
Svendson |
Tove |
Borgvn 23 |
Sandnes |
| 3 |
Pettersen |
Kari |
Storgt 20 |
Stavanger |
| 4 |
Nilsen |
Johan |
Bakken 2 |
Stavanger |
| 5 |
Tjessem |
Jakob |
Nissestien 67 |
Sandnes |
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='Sandnes'
|
The "Persons" table would have looked like this:
| P_Id |
LastName |
FirstName |
Address |
City |
| 1 |
Hansen |
Ola |
Nissestien 67 |
Sandnes |
| 2 |
Svendson |
Tove |
Nissestien 67 |
Sandnes |
| 3 |
Pettersen |
Kari |
Nissestien 67 |
Sandnes |
| 4 |
Nilsen |
Johan |
Nissestien 67 |
Sandnes |
| 5 |
Tjessem |
Jakob |
Nissestien 67 |
Sandnes |
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