Delete query for two way friendship (mysql) - php

Question

Friendship in my DB is a two way street. Check screenshot:
So user id 14 and 1 are friends.
I want a query that can be initiated by either party and that deletes two way street completely removing both rows.
How would I go about doing this? This is not simple WHERE asked asker = id.

Answer 1

Use AND and OR to create a condition from simpler conditions, like
(asker_user_id = 14 AND asked_user_id = 1) OR
(asked_user_id = 14 AND asker_user_id = 1)

Answer 2

DELETE FROM friendship
WHERE (asker_user_id = 14 AND asked_user_id = 1)
OR (asker_user_id = 1 AND asked_user_id = 14)

Answer 3

You could combine 2 IN conditions, to achieve this.
DELETE FROM foo WHERE asker_user_id IN (1, 14) AND asked_user_id IN (1, 14)
http://sqlfiddle.com/#!2/d1866/1

Answer 4

$slq = "SELECT * from Table where `id` = '13' "; //depending on user
$query = mysql_query($sql);
$result = mysql_fetch_array($query);
$asker = $result['asker_user_id']; //14 //
$asked = $result['asked_user_id']; //1
$id = $result['id'];
$del_sql = "DELETE from table WHERE asked_user_id = '.$asker.' AND asker_user_id = '.$asked.'";
$del_query = mysql_query($del_sql);
$del_first = "Delete from table Where `id` = $id";
$del_first_query = mysql_query($del_first);

Answer 5

UPDATED (and tested)
My approach works even if you don't know relationship between 1 and 14. If you are looking for really "(asker = 14 AND asked = 1) OR (asked = 14 AND asker = 1)", it is easy while you are thinking "This is not simple"
Here is what I have tested. I hope this help somebody (including OP). Thanks.
Given Data
CREATE TABLE tab
(
id int,
asker_user_id int,
asked_user_id int
);
insert into tab value(1, 2, 1);
insert into tab value(2, 15, 1);
insert into tab value(3, 14, 1);
insert into tab value(4, 1, 14);
insert into tab value(5, 5, 1);
insert into tab value(6, 1, 5);
insert into tab value(7, 2, 5);
Q1 - find all relationship
SELECT t1.asker_user_id, t1.asked_user_id
FROM tab AS t1 JOIN tab AS t2
WHERE t1.asked_user_id = t2.asker_user_id
AND t2.asked_user_id = t1.asker_user_id
+---------------+---------------+
| asker_user_id | asked_user_id |
+---------------+---------------+
| 1 | 14 |
| 14 | 1 |
| 1 | 5 |
| 5 | 1 |
+---------------+---------------+
Q2 - before delete, check relationship's record id
SELECT DISTINCT A.id as record_id
FROM tab A JOIN
(
// insert Q1 here
) B ON (A.asker_user_id = B.asker_user_id AND A.asked_user_id = B.asked_user_id)
OR (A.asked_user_id = B.asker_user_id AND A.asker_user_id = B.asked_user_id)
+-----------+
| record_id |
+-----------+
| 3 |
| 4 |
| 5 |
| 6 |
+-----------+
Q3 DELETE all friendship record
DELETE A
FROM tab A JOIN
(
// insert Q1 here
) B ON (A.asker_user_id = B.asker_user_id AND A.asked_user_id = B.asked_user_id)
OR (A.asked_user_id = B.asker_user_id AND A.asker_user_id = B.asked_user_id)
Query OK, 4 rows affected (0.00 sec) <== records which has friendship are deleted.
Orig. Answer
Not tested, but I guess it will display both 13 and 14
SELECT *
FROM tab A JOIN
(
SELECT t1.asker_user_id, t2.asked_user_id
FROM tab AS t1 JOIN tab AS t2
WHERE t1.asked_user_id = t2.asker_user_id
AND t2.asked_user_id = t1.asker_user_id
) B ON (A.asker_user_id = B.asker_user_id AND A.asked_user_id = B.asked_user_id)
OR A.asked_user_id = B.asker_user_id AND A.asker_user_id = B.asked_user_id)
when above query works, then delete like this:
DELETE FROM tab
WHERE id IN (
SELECT A.id
FROM tab A JOIN
(
SELECT t1.asker_user_id, t2.asked_user_id
FROM tab AS t1 JOIN tab AS t2
WHERE t1.asked_user_id = t2.asker_user_id
AND t2.asked_user_id = t1.asker_user_id
) B ON (A.asker_user_id = B.asker_user_id AND A.asked_user_id = B.asked_user_id)
OR A.asked_user_id = B.asker_user_id AND A.asker_user_id = B.asked_user_id)
)

Answer 6

Selfjoin:
SELECT *
FROM friendship asker
LEFT JOIN friendship asked
ON asker.asked_user_id = asked.asker_user_id
WHERE asker.asker_user_id IS NOT NULL
I cannot test right now (or just lazy to create an sqlfiddle),
but it is something like this.
I maybe switched asked and asker in a way.
This is the way you can test if you have both (instead of select, use delete, after checking the correct fields)