У меня есть следующий SQL заявление, которое имеет очень плохую производительность:Как улучшить производительность вложенного ЗЕЬЕСТ в MySQL
SELECT
frmInstLastModifiedDate AS last_modified
, frmInstID AS proj_id
, frmInstIsApproved
, frmInstStatus AS proj_sts
, (CASE
WHEN frmInstCreator = 294 THEN 'M'
WHEN status = 'f' THEN 'F'
WHEN (frmInstID IN (SELECT shr.frmInstID from tbl_frm_share as shr WHERE shr.shrMember = 294 AND shr.shrType = 'LIKE' AND shr.frmID = inst.frmID)) THEN 'L'
WHEN (frmInstID IN (SELECT shr.frmInstID from tbl_frm_share as shr WHERE shr.shrMember = 294 AND shr.shrType = 'SHARE' AND shr.frmID = inst.frmID)) THEN 'S'
ELSE 'O' END) as proj_grp
, (SELECT lkpCode FROM tbl_frm_lookup WHERE lkpID = (SELECT ansValue FROM tbl_itm_answer WHERE frmInstID = proj_id AND itmID = (select itmID from tbl_frm_item where itmName = 'prjStatus' AND frmID = inst.frmID))) as prjStatus
, (SELECT lkpCode FROM tbl_frm_lookup WHERE lkpID = (SELECT ansValue FROM tbl_itm_answer WHERE frmInstID = proj_id AND itmID = (select itmID from tbl_frm_item where itmName = 'ProjectType' AND frmID = inst.frmID))) as ProjectType
, (SELECT itmID FROM tbl_itm_answer where itmID in (828,829,830,831) and frmInstID = proj_id AND SUBSTRING(ansValue,1,2) = 'on') as primIRWMObj
, (SELECT lkpCode FROM tbl_frm_lookup WHERE lkpID = (SELECT ansValue FROM tbl_itm_answer WHERE frmInstID = proj_id AND itmID = (select itmID from tbl_frm_item where itmName = 'PrjPSubReg'))) as ProjectSubReg
, frmInstCreator AS proj_creatorID
, frmInstCode AS proj_code
FROM tbl_frm_instance inst
WHERE status not like 'd'
HAVING (proj_sts like 'c' AND ('PROJECT PROPONENT' = 'ADMIN' or proj_creatorID = 294))
or (proj_sts like 'a')
or (proj_sts like 't' AND proj_creatorID = 294)
OR (proj_grp = 'S')
ORDER BY frmInstCreateDate DESC ;
Заявление создается динамически на основе выбранных пользователем параметров. Я знаю, вложенные оператор выбора (например, в следующем) является проблемой, но я не знаю, как я могу заменить его
(SELECT lkpCode FROM tbl_frm_lookup WHERE lkpID = (SELECT ansValue FROM tbl_itm_answer WHERE frmInstID = proj_id AND itmID = (select itmID from tbl_frm_item where itmName = 'prjStatus' AND frmID = inst.frmID))) as prjStatus
любой помощь будет высоко ценятся.
Это трудно настроить производительность SQL без объяснить. Если вы опубликуете план объяснения, мы сможем помочь вам лучше. –