How to Delete Posts Related to a Specific Client Using MySQL Joins?

Deleting Posts Associated with a Specific Client in MySQL

Problem:

Our database contains three tables: clients, projects, and posts. The goal is to remove all posts linked to a particular client. The following SQL statement is ineffective:

<code class="language-sql">DELETE
FROM posts
INNER JOIN projects ON projects.project_id = posts.project_id
WHERE projects.client_id = :client_id;</code>

The posts table lacks a direct client_id foreign key; it only possesses a project_id foreign key.

Solution:

To eliminate posts connected to projects belonging to a specific client, the DELETE statement must target the posts table explicitly. The corrected query is:

<code class="language-sql">DELETE posts
FROM posts
INNER JOIN projects ON projects.project_id = posts.project_id
WHERE projects.client_id = :client_id;</code>

Alternative Solution:

A more efficient method involves implementing an ON DELETE CASCADE constraint when establishing the foreign key relationship between the projects and posts tables. This automatically deletes posts when their associated project is deleted. The revised SQL query becomes:

<code class="language-sql">DELETE FROM projects WHERE client_id = :client_id;</code>

This approach leverages the ON DELETE CASCADE constraint to remove all related posts simultaneously.

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