求SQL语句：从一个表中取出数据作为条件在另一个表取数据。

[weiwei001001]

两张表，一个试题表T_topic,一个抽取试题的条件表T_where
T_topic 的结构： tid,typeid,diff (试题ID，题型ID，难易度ID)
T_where 的结构： id,typeid,diff,num (主键，题型ID，难易度ID，抽取数量)

怎么根据T_ where中的条件抽取试题。

[Mr_Nice]

select *
from t_topic
where exists(select 1 from t_where where t_topic.题型ID = t_where.题型ID)

[shizhu820228]

[Quote=引用 1 楼 的回复:]

SQL code
select *
from t_topic
where exists(select 1 from t_where where t_topic.题型ID = t_where.题型ID)
[/Quote]
＋

[快溜]

select b.* from T_where a
cross apply(select top (a.num) * from T_topic
where typeid=a.typeid and diff=a.diff order by newid()) b

[筱筱澄]

--> 测试数据：[T_topic]
IF OBJECT_ID('[T_topic]') IS NOT NULL DROP TABLE [T_topic]
GO 
CREATE TABLE [T_topic]([试题ID] INT,[题型ID] INT,[难易度ID] VARCHAR(1))
INSERT [T_topic]
SELECT 1,1,'A' UNION ALL
SELECT 2,1,'A' UNION ALL
SELECT 3,1,'A' UNION ALL
SELECT 4,2,'A' UNION ALL
SELECT 5,2,'A' UNION ALL
SELECT 6,1,'B' UNION ALL
SELECT 7,1,'B' UNION ALL
SELECT 8,1,'B' UNION ALL
SELECT 9,1,'B'

--> 测试数据：[T_where]
IF OBJECT_ID('[T_where]') IS NOT NULL DROP TABLE [T_where]
GO 
CREATE TABLE [T_where]([主键] INT,[题型ID] INT,[难易度ID] VARCHAR(1),[抽取数量] INT)
INSERT [T_where]
SELECT 1,1,'A',2 UNION ALL
SELECT 2,2,'A',1 UNION ALL
SELECT 3,1,'B',3
--------------开始查询--------------------------

SELECT a.*,b.[抽取数量] FROM [T_topic]a, [T_where] b
WHERE a.[题型ID]=b.[题型ID] AND a.[难易度ID]=b.[难易度ID] 
AND (select count(*) FROM [T_topic] AS c WHERE  a.[题型ID]=c.[题型ID] AND a.[难易度ID]=c.[难易度ID] AND c.[试题ID]>a.[试题ID])<b.[抽取数量]
----------------结果----------------------------
/* 
试题ID        题型ID        难易度ID 抽取数量
----------- ----------- ----- -----------
3           1           A     2
2           1           A     2
5           2           A     1
9           1           B     3
8           1           B     3
7           1           B     3

(6 行受影响)


*/

[shawN_h]

select a.tid,a.typeid,a.diff,b.typeid
from t_topic a left outer join t_topic b on a.typeid=b.typeid
where b.tpyeid is not null

[问苍天人生几何]

;with cte as
(
	select row_number() over(partition by a.题型,a.难易度ID order by newid()) rn,a.*,b.抽取数量 from T_topic a, T_where b
	where a.题型=b.题型 and a.难易度ID=b.难易度ID
)
select * from cte
where rn<抽取数量

[筱筱澄]

--2005
SELECT DISTINCT b.*
FROM [T_where] AS a
CROSS APPLY
(
    SELECT TOP([抽取数量]) * FROM [T_topic] WHERE  a.[题型ID]=[题型ID] AND a.[难易度ID]=[难易度ID]
     ORDER BY [试题ID]-- NEWID() newid 是随机抽取
) AS b