How to add join based on conditions in mysql

Question

How to set joins based on conditions, I am trying to use if or case for doing this, how can I achieve this. mysql error Code: 1241. Operand should contain 1 column(s)

SET @sUserId = 15;

SELECT userClip.userId
FROM
  ( select if(@sUserId > 0 ,(select * from groups),(select * from otherGroups))folderId)abc
INNER JOIN userClip
on abc.folderId = userClip.folderId

Try to put IF before the SELECT, and use two queries (one per each case), instead of single. — michaJlS, May 30 '16 at 09:26
syntax error if i put if before select, will u give an example of it — pitu, May 30 '16 at 09:29

iLikeMySql · Answer 1 · 2016-05-30T09:54:34.070

0

You could split your condition into two LEFT JOINS. This should work since your @sUserId can't be > and <= 0 at the same time. I also changed userClip to userFolder because it looked like you mixed those up (please give feedback if not).

TWO LEFT_JOINS:

SELECT userFolder.userId
FROM
 userFolder 
LEFT JOIN (SELECT * FROM groups) as abc   
on(@sUserId>0 and abc.folderId = userFolder.folderId)
LEFT JOIN (SELECT * FROM otherGroups) as bcd 
on(@sUserId>=0 and bcd.folderId = userFolder.folderId)

edited May 30 '16 at 09:54

answered May 30 '16 at 09:47

iLikeMySql

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3
7

will try & let you know – pitu May 30 '16 at 09:57

How to add join based on conditions in mysql

1 Answers1