查找从表里面日期最后的一条记录（急）

[coffeedou]

从表b里面有多条记录，里面有时间字段t1，和部门字段d1，和主表a用两个关键字段关联k1,k2，如何查出最近的部门，即时间最靠后的部门呢？
select a.k1,a.k2,b.d1 from a
left join b on a.k1=b.k1 and a.k2=b.k2

[bjt_]

select a.k1,a.k2,b.d1,b.t1 from a, b
where a.k1=b.k1(+) and a.k2=b.k2(+) and b.t1=(select max(t1) from b)

b.t1要建索引

[临摹]

修改下你写的:
select k1,k2,d1 from(
select a.k1,a.k2,b.d1 from a
left join b on a.k1=b.k1 and a.k2=b.k2 order by b.t1 desc)
where rownum=1

[WangZWang]

Select a.k1,a.k2,x.d1 from a
left join b as x on a.k1=x.k1 and a.k2=x.k2
Where not exists(Select * from b Where d1=x.d1 and t1>x.t1)

[coffeedou]

79bo(山芋) ( ) 信誉：100

你这样只能查出一条吧？

WangZWang(先来) ( ) 信誉：100

试了，好象不行

[WangZWang]

Select a.k1,a.k2,x.d1 from a
Inner join b as x on a.k1=x.k1 and a.k2=x.k2
Where not exists(Select * from b Where d1=x.d1 and t1>x.t1)

[临摹]

我以为最靠后的只有一个呢.
要不
select a.k1,a.k2,b.d1 from a
left join b on a.k1=b.k1 and a.k2=b.k2
where b.t1=(select max(t1) from b)

[ksrs]

select a.*,b.*
from a,b
where d1 =
( select max(d1)
from
(
select a.k1,a.k2,b.d1 from a
left join b on a.k1=b.k1 and a.k2=b.k2
)
)
and a,k1 = b.k1 and a.k2 = b.k2;

[shan1119]

select * from (select a.k1,a.k2,b.d1 from a
left join b on a.k1=b.k1 and a.k2=b.k2 order by b.t1 desc) where rownum=1;

[shan1119]

刚看了回复,还是赞同 79bo(山芋) 的.

[shanhqk]

1、b.t1建立索引不管用，因为是时间字段。
2、如果这个表是自己设计的，可以把该字段设置为浮点，然后再建立索引，这样所建立的索引是惯用，可以使用排序的方法。
3、既然：表b里面有多条记录，里面有时间字段t1，和部门字段d1，那么为什么还需要主表a呢，我不是很明白。

[tiaodongdeyinfu]

楼主只是说最靠后，但是不知道有多少条是吧？如果是这样，在表b里面肯定有个时间最大值吧？这样不就能取出最靠后的部门了吗？
select Select a.k1,a.k2,x.d1 from a
left join b as x on a.k1=x.k1 and a.k2=x.k2
where b.t1 = (select max(t1) from b)
这样就行了。

[tiaodongdeyinfu]

错了，是：
select Select a.k1,a.k2,x.d1 from a
left join b as x on a.k1=x.k1 and a.k2=x.k2
where x.t1 = (select max(t1) from b)

[bjt_]

kao,shanhqk(山) ( )
"b.t1建立索引不管用，因为是时间字段。"
建议你再去学学数据库的基础