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SQL Lesson 15: Deleting rows
When you need to delete data from a table in the database, you can use a DELETE statement, which
describes the table to act on, and the rows of the table to delete through the WHERE clause.
Delete statement with condition
DELETE FROM mytable
WHERE condition;
If you decide to leave out the WHERE constraint, then all rows are removed, which is a quick
and easy way to clear out a table completely (if intentional).
Taking extra care
Like the UPDATE statement from last lesson, it's recommended that you run the constraint in a
SELECT query first to ensure that you are removing the right rows. Without a proper backup or test
database, it is downright easy to irrevocably remove data, so always read your DELETE statements
twice and execute once.
Exercise
The database needs to be cleaned up a little bit, so try and delete a few rows in the tasks below.
Table: movies
Exercise 15 — Tasks
- This database is getting too big, lets remove all movies that were released before 2005.
- Andrew Stanton has also left the studio, so please remove all movies directed by him.
Stuck? Read this task's Solution.
Solve all tasks to continue to the next lesson.
Finish above Tasks
Solve all tasks to continue to the next lesson.