我需要改善大型MySQL視圖的性能。其中大部分非常簡單,不會造成太多的性能問題,但是有很長一段時間充滿了數十個子查詢,這些子查詢以相同的問題遞增一個值。我認爲必須有更好的方法來做到這一點,但我不是SQL大師。任何幫助是極大的讚賞!如何減少對這些MySQL子查詢的需求?
(我概括一下代碼,使問題更加清晰)
SELECT
p.something,
p.otherthing,
c.athing,
d.nothing,
(select startdate from dbo.aqcprojects where projectid = p.id and aqcphase = 1) as 'Phase 1 start',
(select finishdate from dbo.aqcprojects where projectid = p.id and aqcphase = 1) as 'Phase 1 end',
(select startdate from dbo.aqcprojects where projectid = p.id and aqcphase = 2) as 'Phase 2 start',
(select finishdate from dbo.aqcprojects where projectid = p.id and aqcphase = 2) as 'Phase 2 end',
**the above four lines repeated ad nauseum.
FROM
bunch of joins
可以顯示錶結構將它添加到一堆? –