MySQL subquery in where clause - mysql

Question

I have a MySQL query which goes like this:
select
*,
(select meta_value
from nord_usermeta m
where meta_key = 'firm' and user_id = s.user_id
limit 1)
as firm,
(select meta_value f
rom nord_usermeta m
where meta_key = 'first_name' and user_id = s.user_id
limit 1)
as first_name,
(select meta_value
from nord_usermeta m
where meta_key = 'last_name' and user_id = s.user_id
limit 1)
as last_name
from nord_submissions s
order by created_at desc
Now I need to narrow it down with a where clause like this:
select
*,
(select meta_value
from nord_usermeta m
where meta_key = 'firm' and user_id = s.user_id
limit 1)
as firm,
(select meta_value
from nord_usermeta m
where meta_key = 'first_name' and user_id = s.user_id
limit 1)
as first_name,
(select meta_value
from nord_usermeta m
where meta_key = 'last_name' and user_id = s.user_id
limit 1)
as last_name
from nord_submissions s
where firm like '%DG%'
order by created_at desc
The problem obviously is in way i use subquery but i cant find a way to reference it in where clause.
Please help.

Answer 1

Why go so Long...try with SELF JOIN ( joining same tables in query )..see below (not tested)
SELECT ns.*,
um1.meta_value AS firmName,
um2.meta_value AS firstName,
um3.meta_value AS lastName
FROM nord_submission ns
INNER JOIN nord_usermeta um1 USING(id) AND meta_key = 'firm'
INNER JOIN nord_usermeta um2 USING(id) AND meta_key = 'first_name'
INNER JOIN nord_usermeta um3 USING(id) AND meta_key = 'last_name'
WHERE um1.meta_value LIKE '%DG%'
ORDER BY ns.created_at
Note: if both table have different column name , by which u refrence each other, then you can replace USING(id) with ns.user_id=um1.user_id and so on

Answer 2

If you're going to use keys rather than columns you'll have to let the application sort it out. Using so many sub-queries you'll see a performance hit.
SELECT *
FROM nord_submissions
INNER JOIN nord_usermeta
USING (user_id)
WHERE (meta_key='last_name' or meta_key='first_name' or (meta_key='firm' and meta_value LIKE '%DG%') )
ORDER BY created_at desc