How to delete from a table interlinking 4 tables - mysql

Question

Hi following are my 4 tables.
client_parent_question :-
+----+------------+------------+---------+-----+------+------+
| id | is_deleted | sort_order | version | cid | pid | qid |
+----+------------+------------+---------+-----+------+------+
| 1 | | 1 | 0 | 1 | 1 | 1 |
| 2 | | 2 | 0 | 1 | 1 | 2 |
| 3 | | 3 | 0 | 1 | 1 | 3 |
| 4 | | 4 | 0 | 1 | 1 | 4 |
| 5 | | 1 | 0 | 1 | 2 | 7 |
+----+------------+------------+---------+-----+------+------+
mysql> select * from client_parent;
+----+------------+------------+---------+-----+------+
| id | is_deleted | sort_order | version | cid | pid |
+----+------------+------------+---------+-----+------+
| 1 | | 1 | 0 | 1 | 1 |
| 2 | | 2 | 0 | 1 | 2 |
+----+------------+------------+---------+-----+------+
2 rows in set (0.00 sec)
mysql> select * from client_question;
+----+------------+---------+-----+------+------+
| id | is_deleted | version | cid | pqid | qtid |
+----+------------+---------+-----+------+------+
| 1 | | 0 | 1 | 1 | 1 |
| 2 | | 0 | 1 | 2 | 4 |
| 3 | | 0 | 1 | 2 | 4 |
| 4 | | 0 | 1 | 1 | 1 |
| 5 | | 0 | 1 | 2 | 4 |
| 6 | | 0 | 1 | 3 | 4 |
| 7 | | 0 | 1 | 3 | 4 |
| 8 | | 0 | 1 | 1 | 1 |
| 9 | | 0 | 1 | 2 | 4 |
| 10 | | 0 | 1 | 3 | 4 |
| 11 | | 0 | 1 | 4 | 4 |
| 12 | | 0 | 1 | 4 | 4 |
+----+------------+---------+-----+------+------+
mysql> select * from client_question_option;
+----+------------+---------+------+------+
| id | is_deleted | version | cqid | oid |
+----+------------+---------+------+------+
| 1 | | 0 | 2 | 1 |
| 2 | | 0 | 3 | 4 |
| 3 | | 0 | 6 | 2 |
| 4 | | 0 | 7 | 3 |
| 5 | | 0 | 11 | 1 |
| 6 | | 0 | 12 | 4 |
| 7 | | 0 | 14 | 1 |
| 8 | | 0 | 15 | 4 |
+----+------------+---------+------+------+
I know only cid and pid of client_parent table
My aim is to delete all from client_question,client_parent_question and client_question_option
In the client_question_option cqid id is the id of client_question table
Following is the sqlfiddle
I did
DELETE FROM cqo,qo,cpq client_question_option cqo ,client_question cq,client_parent_question ,client_parent cp
WHERE cqo.cqid=cq.id AND cq.pqid=pq.id AND cqo.oid=qo.id AND cq.cid=1 AND cp.pid=1
But this did not work.

Answer 1

You just need to move the FROM keyword after the table aliases. See multiple-table syntax
DELETE cqo, qo, cpq
FROM client_question_option cqo,
client_question cq,
client_parent_question,
client_parent cp
WHERE cqo.cqid=cq.id AND cq.pqid=pq.id AND cqo.oid=qo.id
AND cq.cid=1 AND cp.pid=1;

Answer 2

Your DELETE query's syntax is wrong, which must be somthing like this:-
DELETE cqo,cp,pq
FROM client_question_option cqo, client_question cq, client_parent_question pq, client_parent cp
WHERE cqo.cqid=cq.id AND cq.pqid=pq.id AND cqo.oid=cp.id AND cq.cid=1 AND cp.pid=1;
Hope this will help you.

Answer 3

using inner join
DELETE cqo,cq,cp,pq
FROM client_question_option cqo
INNER JOIN client_question cq
INNER JOIN client_parent_question as pq
INNER JOIN client_parent cp
WHERE cqo.cqid=cq.id AND cq.pqid=pq.id AND cqo.oid=cqo.id AND cq.cid=1 AND cp.pid=1

Answer 4

You have an option in MYSQL Called as ONDELETE CASCADE where in when you set this on a key
example : foreign key(cid) references client_parent(cid) ON DELETE CASCADE when you delete the key based on your condition all referencing ids will be deleted , so one simple query to delete parent row is enough for it to delete all child rows present in other table data
Advantages of using ON DELETE CASCADE
you are not require to right innerjoins and delete data manually
you dont get parent key errors
you can save up your time
Thats it NJOY!!!