Delete with Join in MySQL

Here is the script to create my tables:

CREATE TABLE clients (
   client_i INT(11),
   PRIMARY KEY (client_id)
);
CREATE TABLE projects (
   project_id INT(11) UNSIGNED,
   client_id INT(11) UNSIGNED,
   PRIMARY KEY (project_id)
);
CREATE TABLE posts (
   post_id INT(11) UNSIGNED,
   project_id INT(11) UNSIGNED,
   PRIMARY KEY (post_id)
);

In my PHP code, when deleting a client, I want to delete all projects posts:

DELETE 
FROM posts
INNER JOIN projects ON projects.project_id = posts.project_id
WHERE projects.client_id = :client_id;

The posts table does not have a foreign key client_id, only project_id. I want to delete the posts in projects that have the passed client_id.

This is not working right now because no posts are deleted.

You just need to specify that you want to delete the entries from the posts table:

DELETE posts
FROM posts
INNER JOIN projects ON projects.project_id = posts.project_id
WHERE projects.client_id = :client_id

EDIT: For more information you can see this alternative answer

Since you are selecting multiple tables, The table to delete from is no longer unambiguous. You need to select:

DELETE posts FROM posts
INNER JOIN projects ON projects.project_id = posts.project_id
WHERE projects.client_id = :client_id

In this case, table_name1 and table_name2 are the same table, so this will work:

DELETE projects FROM posts INNER JOIN [...]

You can even delete from both tables if you wanted to:

DELETE posts, projects FROM posts INNER JOIN [...]

Note that order by and limit don't work for multi-table deletes.

Also be aware that if you declare an alias for a table, you must use the alias when referring to the table:

DELETE p FROM posts as p INNER JOIN [...]

^{Contributions from Carpetsmoker and etc.}

Delete with Join in MySQL

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