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HomeDatabaseMysql Tutorial10分钟小幅优化亿级数据查询

前几天,一个用户研发QQ找我,如下: 自由的海豚。 16:12:01 岛主,我的一条SQL查不出来结果,能帮我看看不? 兰花岛主 16:12:10 多久不出结果? 自由的海豚 16:12:17 多久都没出结果,一直没看到结果过。 兰花岛主 16:12:26 呵呵,好。 兰花岛主 16:12:39

前几天,一个用户研发QQ找我,如下:

自由的海豚。 16:12:01

岛主,我的一条SQL查不出来结果,能帮我看看不?

兰花岛主 16:12:10

多久不出结果?

自由的海豚 16:12:17

多久都没出结果,一直没看到结果过。

兰花岛主 16:12:26

呵呵,好。

兰花岛主 16:12:39

发下sql和执行计划。

自由的海豚 16:12:55

select n.c1, n.c2,n.c3,n.c4,n.c5
from (select count(t.c1), t.c1, t.c2,t.c3,t.c4,t.c5
from tab1 t
where t.c2 not in ('val1','val2','val3','val4','val5')
group by t.c1, t.c2,t.c3,t.c4,t.c5) n
where not exists
(select * from (
select count(s.c2), s.c1, s.c2
from (select m.c1, m.c2,m.c3,m.c4,m.c5
from tab1 m
where exists (select c1
from tab2 n
where c2 > sysdate - 14
and m.c1 = n.c1)
and m.c1 is not null
and m.c2 not in ('val1','val2', 'val3', 'val4', 'val5')) s
group by s.c1, s.c2) t1 where t1.c2 = n.c2)
and n.c1 is not null;

\

兰花岛主 16:13:12

这两张表大吗?

自由的海豚 16:13:16

tab1小,tab2亿级以上,两周数据在几千万。

兰化岛主 16:13:22

OK。

兰花岛主 16:16:29

这么改下sql吧:

with t1 as(
select count(t.c1), t.c1,t.c2,t.c3,t.c4,t.c5
from tab1 t
where t.c2 not in ('val1','val2','val3','val4','val5')
and c1 is not null
group by t.c1, t.c2,t.c3,t.c4,t.c5)
select t1.c1,t1.c2,t1.c3,t1.c4,t1.c5
from t1
where not exists(
select /*+ use_hash(m,n)*/ m.c1, m.c2,m.c3,m.c4,m.c5
from t1 m,tab2 n
where n.c2 > sysdate - 14
and m.c1 = n.c1
and t1.c2 = m.c2);

兰花岛主 16:16:43

取下执行计划。

自由的海豚 16:16:57

好的。

自由的海豚 16:17:25

\

兰花岛主 16:17:57

好的,试试吧。

自由的海豚 16:19:28

出结果了,37s

 

兰花岛主 17:20:21

嗯,好。

兰花岛主 17:20:34

这样可以吗?

自由的海豚 17:20:47

可以了可以了

兰花岛主 17:21:11

嗯,好,那就先这样,不继续调了。

自由的海豚 17:21:30

恩 好的 谢谢岛主

兰花岛主 17:21:53

不客气,忙吧,有事儿联系。

自由的海豚 17:22:18

恩,您忙。。。

至此,对用户这个sql的优化结束,其实,这个语句应该还有优化的空间,只是,用户说可以了那就可以了,因为优化是无止境的,而且,更进一步优化也许会需要更进一步的信息,且有时会需要更大的改动,鉴于各方面因素,文中对语句和计划进行了处理,记录于此,共勉!

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