高分:含千万条数据的表查询的性能问题
A表：
symbol tdate tclose
000001 20070725 1.23
000002 20070726 0.23
000001 20070723 2.3
000004 20070618 1.4
B表:
symbol
000001
000002
000004
输入2007-07-26
输出
symbol tdate tclose lclose
000001 20070725 1.23 2.3
000002 20070726 0.23 NULL
000004 20070618 1.4 NULL
symbol从B表中取现出,tdate为最新的tclose,
lclose为第二新的tclose,
tclose不为0或NULL
A表的记录数为2000万条左右,现在主要是一个效率的问题.不知道怎么才能再快点.
[解决办法]
说说现在的索引情况
[解决办法]
语句：
select x.*,y.tclose as lclose
from a x left join a y
on a.symbol=b.symbol
and b.tdate=(select max(tdate) from a where symbol=a.symbol and tdate <a.tdate)
where a.tdate <=cast( '2007-7-26 ' as datetime)
and a.tclose <> 0 and a.tclose is not NULL
and not exists (
select 1 from a where symbol=a.symbol
and tdate <=cast( '2007-7-26 ' as datetime)
and tclose <> 0 and tclose is not NULL
and tdate> a.tdate
)
最好有索引(symbol,tdate,tclose)
[解决办法]
晕,我写错了
语句：
select x.*,y.tclose as lclose
from a x left join a y
on x.symbol=y.symbol
and y.tdate=(select max(tdate) from a where symbol=x.symbol and tdate <x.tdate)
where x.tdate <=cast( '2007-7-26 ' as datetime)
and x.tclose <> 0 and x.tclose is not NULL
and not exists (
select 1 from a where symbol=x.symbol
and tdate <=cast( '2007-7-26 ' as datetime)
and tclose <> 0 and tclose is not NULL
and tdate> x.tdate
)
最好有索引(symbol,tdate,tclose)
[解决办法]
要有索引(symbol,tdate,tclose)
[解决办法]
看看这贴，问问这位兄弟
http://community.csdn.net/Expert/topic/5673/5673596.xml?temp=.3719904
[解决办法]
问题没看明白。lclose怎么定义的？
[解决办法]
试试这个.
------------------------------------------------
create table #t (
symbol varchar(10),
tdate varchar(10),
tclose numeric(8,2),
lclose numerice(8,2))
insert #t(symbol,tdate,tclose)
select a.symbol,max(tdate),tclose from a,b where a.symbol=b.symbol
group by a.symbol,tclose
create index idx_t_symbol_tdate on #t (symbol,tdate)
update #t set lclose = b.tclose from a b
where #t.symbol=b.symbol and b.tdate < #t.tdate and not exists (select * from a where a.symbol=b.symbol and a.tdate> b.tdate)
select * from #t
drop table #t
[解决办法]
不知道你的有多慢,有的时候由于数据多,同时硬件和sql优化不是很好的话,是慢的.
[解决办法]
楼主是求某一天的,那把下面那句换下.
insert #t(symbol,tdate,tclose)
select a.symbol,max(tdate),tclose from a,b where a.symbol=b.symbol
group by a.symbol,tclose
换成
-------------------------------
insert #t(symbol,tdate,tclose)
select a.symbol,tdate,tclose from a,b where a.symbol=b.symbol
where a.tdate=replace( '2006-07-26 ', '- ', ' ')
[解决办法]
直接在查询分析器里“显示执行计划“，然后根据执行计划里耗时情况来创建索引，如果还不行，就用索引优化向导，这样就可以了。
[解决办法]
上边的有错误,重新贴个完整的.
--------------------------------------------
set nocount on
create table #t (
symbol varchar(10),
tdate varchar(10),
tclose numeric(8,2),
lclose numeric(8,2))
insert #t(symbol,tdate)
select a.symbol,tdate from a,b
where a.symbol=b.symbol
and a.tdate=replace( '2007-07-26 ', '- ', ' ')
create index idx_t_symbol_tdate on #t (symbol,tdate)
update #t set tclose = a.tclose from a where #t.symbol=a.symbol and #t.tdate=a.tdate
update #t set #t.lclose = c.tclose from a c
where #t.symbol=c.symbol and c.tdate < #t.tdate and not exists (select * from a where a.symbol=c.symbol and a.tdate> c.tdate
and a.tdate <> #t.tdate)
select * from #t
drop table #t
drop table a
drop table b
set nocount off
[解决办法]
笔误,习惯了.
上面的
drop table a
drop table b
是多余的.
[解决办法]
不好意思 我想问下怎么才能提问？
[解决办法]
到小类去提问.
