Delete with Join in MySQL

Or the same thing, with a slightly different (IMO friendlier) syntax:

DELETE FROM posts 
USING posts, projects 
WHERE projects.project_id = posts.project_id AND projects.client_id = :client_id;

BTW, with mysql using joins is almost always a way faster than subqueries...

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 [...]

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^{Contributions from Carpetsmoker and etc.}

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

You can also use ALIAS like this it works just used it on my database! t is the table need deleting from!

DELETE t FROM posts t
INNER JOIN projects p ON t.project_id = p.project_id
AND t.client_id = p.client_id