Slide 14.12: SQL delete and drop statements

Slide 14.11: SQL update statement
Slide 14.13: Programming Exercise IV SQL commands
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SQL Delete and Drop Statements

The DELETE statement is used to delete rows in a table. Notice the where clause in the delete syntax. The where clause specifies which records that should be deleted. If you omit the where clause, all records will be deleted!

Assume the Persons table is given below:

 DELETE FROM  table_name
   WHERE  column_name = 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	Nina	Stien 12	Stavanger

 DELETE FROM  Persons  WHERE  LastName = 'Rasmussen';
 DELETE FROM  Persons;

The first delete statement deletes “Nina 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

The second delete statement deletes all rows in the Persons table without deleting the table. This means that the table structure, attributes, and indexes will be intact.

P_Id	LastName	FirstName	Address	City

The DROP TABLE command is to delete a table (the table structure, attributes, and indexes will also be deleted):

 DROP  TABLE  table_name

Demonstration
Below is an SQL test area from W3Schools, which uses the well-known Northwind sample database. The tables here are for read only because of the problem of embedding the scripts. For a fully working example, check this by using Chrome.

Result:

The Database includes:

Tablename	Record
Customers	91
Categories	8
Employees	10
OrderDetails	518
Orders	196
Products	77
Shippers	3
Suppliers	29

W3C WebSQL

WebSQL Browser Support