Left join Without Subqueries

Question

I am getting the below output, I want the same out but without subqueries .I am looking to refine the below query by removing the subquery as it is affecting the performance of the application. Could anyone help me to remove subquery and fetch the required data using the joins.

SELECT DISTINCT rec.requestno as requestno
    , (SELECT min(dateandtime) 
       from recruitersubmission 
       where recruitersubmission.requestno = rec.requestno) as firstsubmsion
    , (SELECT max(dateandtime) 
       from recruitersubmission 
       where recruitersubmission.requestno = rec.requestno) as lastsubmission
    , cndinterview.dateandtime as  candidatefedtime
    , cndinterview.dateandtime AS recruitertime
    , CONCAT(availabledate,' ', availabletime) AS candidateavaibledatetime
    , cndfeedback.status AS status
    , cndfeedback.offereddate AS offereddate
    , cnd.status AS onboard
    , (SELECT COUNT(recruitersubmission.requestno)
       FROM recruitersubmission 
       WHERE recruitersubmission.requestno=rec.requestno) AS totalSub
    , (select COUNT(candidatefeedback.requestno) 
       from candidatefeedback 
       WHERE candidatefeedback.requestno = rec.requestno 
          && candidatefeedback.status = 'Selected' ) as totalsel
    , (select COUNT( candidatefeedback.requestno) 
       from candidatefeedback 
       WHERE candidatefeedback.requestno = rec.requestno 
          && cndfeedback.status = 'Rejected' ) as totalrej
    , (select COUNT(candidatefeedbkonboard.requestno) 
       from candidatefeedbkonboard 
       WHERE candidatefeedbkonboard.requestno = rec.requestno 
          && cnd.status = 'Drop' ) as totaldrop
    , (select COUNT(candidatefeedbkonboard.requestno) 
       from candidatefeedbkonboard 
       WHERE candidatefeedbkonboard.requestno = rec.requestno 
          && candidatefeedbkonboard.status = 'Onboarded' ) as totalonboard
from recruitersubmission AS rec 
LEFT JOIN candidatefeedbkonboard AS cnd 
    ON rec.requestno=cnd.requestno 
LEFT JOIN candidatefeedback AS cndfeedback 
    ON rec.requestno=cndfeedback.requestno 
LEFT JOIN candidatesinterview AS cndinterview 
    ON rec.requestno=cndinterview.requestno
where rec.clientname = '$client' 
   && rec.requestno != ''  
   && rec.country = '$location' 
   && date(rec.dateandtime) between '$fromdate'

I want to avoid these below subqueries.

(select COUNT(candidatefeedback.requestno) from candidatefeedback WHERE candidatefeedback.requestno = rec.requestno && candidatefeedback.status = 'Selected' ) as totalsel

Answer 1

Thank you for the help friends. I figured out how to do it. Below is the solution for your refernce.

SELECT
    rec.requestno,
    COALESCE(totalsub, 0) AS totalsub,
    COALESCE(totalsel, 0) AS totalsel,
    COALESCE(totalrej, 0) AS totalrej
FROM recruitersubmission rec
LEFT JOIN (
    SELECT requestno, COUNT(*) AS totalsub
    FROM recruitersubmission
    GROUP BY requestno
) recruitersubmission  ON recruitersubmission.requestno = rec.requestno
LEFT JOIN (
    SELECT  requestno,count(if(status = 'Selected',1,Null)) AS totalsel,count(if(status = 'Rejected',1,Null)) as totalrej
    FROM candidatefeedback 
    GROUP BY requestno
) candidatefeedback  ON candidatefeedback.requestno = rec.requestno


GROUP by rec.requestno Limit 0,25

Answer 2

Re: your subqueries:

(SELECT min(dateandtime) from recruitersubmission where recruitersubmission.requestno = rec.requestno)

Needs INDEX(requestno, dateandtime) . Similarly for other subqueries.

Re: Seejith's answer:

count(if(status = 'Selected',1,Null))

Can be replaced by

SUM(status = 'Selected')

thereby eliminating the need for COALESCE(.., 0) .