Data Manipulation Language

Read this chapter and take notes on the purpose and use of the clause SELECT and how the INSERT and DELETE statements are used to make changes to data. Also, note how functions are used in these statements.

DELETE statement

The DELETE statement removes rows from a record set. DELETE names the table or view that holds the rows that will be deleted and only one table or row may be listed at a time. WHERE is  a standard WHERE clause that limits the deletion to select records.

The DELETE syntax looks like this.

DELETE [FROM] {table_name | view_name }
[WHERE clause]

The rules for the DELETE statement are:

  1. If you omit a WHERE clause, all rows in the table are removed (except for indexes, the table, constraints).
  2. DELETE cannot be used with a view that has a FROM clause naming more than one table. (Delete can affect only one base table at a time.)

What follows are three different DELETE statements that can be used.

1. Deleting all rows from a table.

DELETE
FROM Discounts

2. Deleting selected rows:

DELETE
FROM Sales
WHERE stor_id = '6380'

3. Deleting rows based on a value in a subquery:

DELETE FROM Sales
WHERE title_id IN
(SELECT title_id FROM Books WHERE type = 'mod_cook')