Slide 7.10: SQL where clause
Slide 7.12: SQL delete and drop statements
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SQL Update Statement

The UPDATE statement is used to update existing records in a table. 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! Assume the Persons table is given below: 
 UPDATE  table_name
   SET column1=value, column2=value2, ...
   WHERE some_column=some_value

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 Rasmussen   Storgt 67   

 UPDATE  Persons  SET  FirstName = 'Nina'
   WHERE  LastName = 'Rasmussen';
 UPDATE  Persons
   SET Address = 'Nissestien 67', City = 'Sandnes';

The result tables from the above two updates are shown below:

  • The first update adds a first name to the person with a last name of “Rasmussen.”
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 Rasmussen Nina Storgt 67  

  • The second update is without a where clause. Thus, all records are updated.
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 Rasmussen Nina Nissestien 67 Sandnes


Demonstration
The following is an SQL test area from W3Schools, which uses the well-known Northwind sample database and the tables are for read only.
For security reasons, the following demonstration may only work in Chrome.

SQL Statement:

Edit the SQL statement and click     to see the result, or    

Result:

Click “Run SQL” to execute the SQL statement above.
W3Schools has created an SQL database in your browser.
The menu to the right displays the database, and will reflect any changes.
Feel free to experiment with any SQL statement.
You can restore the database at any time.
The Database includes:
The Database includes:

TablenamesRecords
Customers91
Categories8
Employees10
OrderDetails518
Orders196
Products77
Shippers3
Suppliers29