I have a query which uses a few left joins to bring back data. The dilemma is that i want to LIMIT
and also ORDER BY
the results from one of the left joins and thus limiting the total numbers of rows brought back.
The table i am trying to order and limit is table4
My query:
SELECT SQL_CALC_FOUND_ROWS e.meta_1, a.requestid, b.clientid, c.job_description, d.forename
FROM quotations_request AS a
LEFT JOIN table1 AS b ON (a.assigned_to = b.userid)
LEFT JOIN table2 AS c ON (a.job_costing = c.jobid)
LEFT JOIN table3 AS d ON (a.clientid = d.clientid)
LEFT JOIN table4 AS e ON (e.quotationid = a.requestid)
WHERE a.archived = '0' AND (e.meta_1 = LCASE('requested') )
What i have tried:
SELECT SQL_CALC_FOUND_ROWS statuss.meta_1, a.requestid, b.clientid, c.job_description, d.forename,
FROM quotations_request AS a
LEFT JOIN table1 AS b ON (a.assigned_to = b.userid)
LEFT JOIN table2 AS c ON (a.job_costing = c.jobid)
LEFT JOIN table3 AS d ON (a.clientid = d.clientid)
LEFT JOIN (Select meta_1 from table4 where quotationid = a.requestid ORDER BY uploaded_date DESC LIMIT 0, 1)
as statuss ON (statuss.quotationid = a.requestid)
WHERE a.archived = '0' AND (statuss.meta_1 = LCASE('requested') )
The result:
After trying the above I got an error saying a.requestid
is unkown in the where clause ( for the last left join)
Try this:
SELECT SQL_CALC_FOUND_ROWS statuss.meta_1, a.requestid, b.clientid, c.job_description, d.forename
FROM quotations_request AS a
LEFT JOIN table1 AS b ON (a.assigned_to = b.userid)
LEFT JOIN table2 AS c ON (a.job_costing = c.jobid)
LEFT JOIN table3 AS d ON (a.clientid = d.clientid)
LEFT JOIN (
select *
from (select
t.*,
@rn := if(quotationid = @qid, @rn + 1,
if(@qid := quotationid, 1, 1)
) rn
from (
select *
from table4
order by quotationid, uploaded_date desc) t cross join (
select @rn := 0, @qid := -1
) t2
) t where rn = 1
)
as statuss ON (statuss.quotationid = a.requestid)
WHERE a.archived = '0' AND (statuss.meta_1 = LCASE('requested') )
The user variables @rn and @qid are used to find the top 1 row from table4 with latest uploaded_date and then join it with the other tables