优化查询（索引、解释）Mysql
根据stackoverflow上另一位开发人员的建议，我已经更新了我的查询，如下所示，但我仍然需要进一步优化它。是否有人可以指导我如何最好地将索引应用于查询 请参阅下面的查询：优化查询（索引、解释）Mysql,mysql,datetime,indexing,query-optimization,in-clause,Mysql,Datetime,Indexing,Query Optimization,In Clause,根据stackoverflow上另一位开发人员的建议，我已经更新了我的查询，如下所示，但我仍然需要进一步优化它。是否有人可以指导我如何最好地将索引应用于查询 请参阅下面的查询： SELECT a.id, a.user_unique_id, a.loan_location, a.ippis, a.tel_no, a.organisation, a.branch, a.loan_agree, a.loan_type, a.appr, a
SELECT a.id, a.user_unique_id, a.loan_location,
a.ippis, a.tel_no,
a.organisation, a.branch, a.loan_agree,
a.loan_type, a.appr, a.sold,
a.loan_status, a.top_up, a.current_loan,
a.date_created, a.date_updated, c.loan_id, c.user_unique_id AS tu_user_unique_id,
c.ippis AS tu_ippis, c.top_up_approved,
c.loan_type AS tu_loan_type, c.dse, c.status, c.current_loan AS tu_current_loan,
c.record_category, c.date_created AS tu_date_created,
c.date_updated AS tu_date_updated
FROM loan_applications_tbl a
LEFT JOIN topup_or_reapplication_tbl c
ON a.ippis=c.ippis
WHERE ((c.status IN ('pending', 'corrected', 'Rejected', 'Processing', 'Captured', 'Reviewed', 'top up')
AND MONTH(CURRENT_DATE) IN (MONTH(c.date_created), MONTH(c.date_updated)
AND YEAR(CURRENT_DATE) IN (YEAR(c.date_created), YEAR(c.date_updated))
AND c.current_loan='1' ))
OR ( a.loan_status IN ('pending', 'corrected', 'Rejected', 'Processing', 'Captured', 'Reviewed', 'top up')
AND MONTH(CURRENT_DATE) IN (MONTH(a.date_created), MONTH(a.date_updated)) )
AND YEAR(CURRENT_DATE) IN (YEAR(a.date_created), YEAR(a.date_updated))
AND (a.current_loan='1'
OR (a.current_loan='0'
AND a.loan_status IN('Approved','Closed')))))
aaippiaacIPPIc或ac状态、日期和当前贷款acaccacc我希望这是可以理解的我一直忘记这个词，因为我很少提到它，但无论如何，您的索引不能通过使用月（）和年（）进行优化因为它们是基础数据上的函数。通过应用日期范围，它们可以。因此，您可以保留您的月/年，例如在2021年1月创建并在2021年3月更新，但另外，添加
"c.date\u created>=当前日期和当前日期，where子句中的或正在以一种可怕的方式破坏性能。有几件事可以让查询运行得更快，但是或必须要去做。@matigo非常感谢你的帮助。你介意帮我用一个可能替代的伪代码吗？你的query在你第一个月（）的测试中有一个错误的位置，应该是你单身的第二个月（c.date_updated）。然后，在您的或条件之前删除一个。@DRapp感谢您的帮助highlight@matigo仍然期待着来自世界各地的帮助you@Peter，请参阅我的修订答案，以获得更多详细的澄清和评论。@Peter，2更多，请参阅修订单词是@Peter，修订为包装（创建或更新）和其他内容query@Peter,请参阅底部的修订，并重新阅读有关howFarBack上下文的整个SQL。
WHERE > beginning of this month and LESS than beginning of next month
loan_applications_tbl ( date_created, date_updated, loan_status, current_loan, ippis )
topup_or_reapplication_tbl ( ippis, status, current_loan, date_created, date_updated )
SELECT
a.id,
a.user_unique_id,
a.loan_location,
a.ippis,
a.tel_no,
a.organisation,
a.branch,
a.loan_agree,
a.loan_type,
a.appr,
a.sold,
a.loan_status,
a.top_up,
a.current_loan,
a.date_created,
a.date_updated,
c.loan_id,
c.user_unique_id tu_user_unique_id,
c.ippis tu_ippis,
c.top_up_approved,
c.loan_type tu_loan_type,
c.dse,
c.status,
c.current_loan tu_current_loan,
c.record_category,
c.date_created tu_date_created,
c.date_updated tu_date_updated
FROM
-- this creates inline mySQL variables I can use for the WHERE condition
-- by doing comma after with no explicit join, it is a single row
-- and thus no Cartesian result, just @variables available now
( select
-- first truncating any TIME portion by casting to DATE()
@myToday := date(curdate()),
@howFarBack := date_sub( @myToday, interval 6 month ),
-- now subtract day of month -1 to get first of THIS month
@beginOfMonth := date_sub( @myToday, interval dayOfMonth( @myToday ) -1 day ),
-- and now, add 1 month for beginning of next
@beginNextMonth := date_add( @beginOfMonth, interval 1 month ) ) SqlVars,
loan_applications_tbl a
LEFT JOIN topup_or_reapplication_tbl c
ON a.ippis = c.ippis
AND c.current_loan='1'
AND c.status IN ('pending', 'corrected', 'Rejected',
'Processing', 'Captured', 'Reviewed', 'top up')
AND
(
(@beginOfMonth <= c.date_created
AND c.date_created < @beginNextMonth)
OR
(@beginOfMonth <= a.date_updated
AND a.date_updated < @beginNextMonth )
)
WHERE
-- forces only activity for the single month in question
-- since the "a" table knows of any "updates" to the "C",
-- its updated basis will keep overall restriction to any accounts
-- updated within this month in question only
-- testing specifically for created OR updated within the
-- current month in question
a.date_created >= @howFarBack
AND
(
(@beginOfMonth <= a.date_created
AND a.date_created < @beginNextMonth)
OR
(@beginOfMonth <= a.date_updated
AND a.date_updated < @beginNextMonth )
)
-- and NOW we can easily apply the OR without requiring
-- to run against the ENTIRE set of BOTH tables.
AND (
c.ippis IS NOT NULL
OR
( a.loan_status IN ( 'pending', 'corrected', 'Rejected', 'Processing',
'Captured', 'Reviewed', 'top up')
AND (
a.current_loan = '1'
OR ( a.current_loan = '0'
AND a.loan_status IN ('Approved', 'Closed')
)
)
)
)