MySQL 'if exists' error

Question

I got a error in my MySQL query:

if not exists(select * from tb_user where user_id=1) then
     select 'ok' as rul;
else
     select 'not' as rul;
end if;

Where's my problem?

You may also want to check on this [performance of count(*) vs exisits post](http://stackoverflow.com/questions/5264658/is-exists-more-efficient-than-count0) to embark in the best solution for you. :) — bonCodigo, Dec 21 '12 at 07:49

score 4 · Answer 1 · answered Dec 21 '12 at 07:28

4

The IF statement can only be used in stored functions. You can do what you want with the IF() function, as follows:

SELECT IF(EXISTS(select * from tb_user where user_id=1), 'ok', 'not') as rul;

answered Dec 21 '12 at 07:28

tom

bonCodigo · Accepted Answer · 2012-12-21T07:41:05.053

3

Another method: You may also use case when

Select case
when exists(select * from tb_user where user_id=1)
then 'Ok'
else 'Not'
end
;

* SQLFiddle Demo

Sample table:

ID  NAME
1   john
2   tim
3   jack
4   rose

Query: renamed the columns as Status

Select case
when exists(select * from table1 where id=1)
then 'Ok'
else 'Not'
end as Status
;

Results:

STATUS
Ok

edited Dec 21 '12 at 07:41

answered Dec 21 '12 at 07:34

bonCodigo

score 1 · Answer 3 · answered Dec 21 '12 at 07:33

1

SELECT IF(COUNT(*) > 0, 'ok', 'not') rul FROM tb_user WHERE user_id = 1;

answered Dec 21 '12 at 07:33

Devart