explain ANALYZE
SELECT count(1)
FROM QbPaper qb
inner JOIN QbPapertype qp ON qb.papertypeId= qp.papertypeId
LEFT JOIN QbSubject qs ON qb.subjectId = qs.subjectId
LEFT JOIN QbExam qe ON qb.paperId=qe.paperId
WHERE 1=1
AND qb.paperAuditstatus = 'Y'
AND qb.classId='CLASS20190716060000000014'
AND qp.papertypeAvlstatus = 'Y'
AND qb.paperAvlstatus='Y'
AND qb.paperPublicstatus='S'
AND qb.paperDelstatus='N'
AND qp.papertypeCode='LNZT'
ORDER BY qb.paperCreateddate desc, qb.paperId DESC