How Can I Efficiently Delete Data from Multiple MySQL Tables Simultaneously?

Deleting Data from Multiple Tables Simultaneously with MySQL

When managing a database with multiple tables related to a specific entity, it becomes necessary to delete all relevant data when removing that entity. The question arises: can we do this efficiently without executing multiple DELETE statements?

The answer lies in MySQL's support for multi-table DELETE operations. The manual explains:

You can specify multiple tables in a DELETE statement to delete rows from one or more tables based on specific conditions in the WHERE clause.

This feature allows us to delete data from multiple tables simultaneously using a single query. Let's revisit the example provided in the question:

DELETE FROM table1 WHERE user_id='$user_id';
DELETE FROM table2 WHERE user_id='$user_id';
DELETE FROM table3 WHERE user_id='$user_id';
DELETE FROM table4 WHERE user_id='$user_id';

Instead, we can rewrite this query as follows:

DELETE t1, t2, t3, t4 FROM t1 INNER JOIN t2 ON t1.user_id=t2.user_id
INNER JOIN t3 ON t2.user_id=t3.user_id INNER JOIN t4 ON t3.user_id=t4.user_id
WHERE t1.user_id='user_id_to_delete';

By utilizing the INNER JOIN keyword, we link the tables based on the common field user_id. The WHERE clause specifies the user ID of the data to be deleted. This query effectively deletes all rows related to the specified user ID from all four tables in a single operation.

It's important to note that the use of ORDER BY or LIMIT is not allowed in multi-table DELETE statements, as these operations are specific to a single table and would affect the deletion sequence. Additionally, the user must have the required permissions to delete data from all the specified tables.

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