Delete with Join in MySQL

Question

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(         


        

Answer 1

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.}

Answer 2

Single Table Delete:

In order to delete entries from posts table:

DELETE ps 
FROM clients C 
INNER JOIN projects pj ON C.client_id = pj.client_id
INNER JOIN posts ps ON pj.project_id = ps.project_id
WHERE C.client_id = :client_id;

In order to delete entries from projects table:

DELETE pj 
FROM clients C 
INNER JOIN projects pj ON C.client_id = pj.client_id
INNER JOIN posts ps ON pj.project_id = ps.project_id
WHERE C.client_id = :client_id;

In order to delete entries from clients table:

DELETE C
FROM clients C 
INNER JOIN projects pj ON C.client_id = pj.client_id
INNER JOIN posts ps ON pj.project_id = ps.project_id
WHERE C.client_id = :client_id;

---

Multiple Tables Delete:

In order to delete entries from multiple tables out of the joined results you need to specify the table names after DELETE as comma separated list:

Suppose you want to delete entries from all the three tables (posts,projects,clients) for a particular client :

DELETE C,pj,ps 
FROM clients C 
INNER JOIN projects pj ON C.client_id = pj.client_id
INNER JOIN posts ps ON pj.project_id = ps.project_id
WHERE C.client_id = :client_id

Answer 3

mysql> INSERT INTO tb1 VALUES(1,1),(2,2),(3,3),(6,60),(7,70),(8,80);

mysql> INSERT INTO tb2 VALUES(1,1),(2,2),(3,3),(4,40),(5,50),(9,90);

DELETE records FROM one table :

mysql> DELETE tb1 FROM tb1,tb2 WHERE tb1.id= tb2.id;

DELETE RECORDS FROM both tables:

mysql> DELETE tb2,tb1 FROM tb2 JOIN tb1 USING(id);

Answer 4

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...

Answer 5

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

Answer 6

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