一道SQL题目的收录

有一个试题表：T_EXAM {ID,type(1,2,3/表示试题类型)，difficulty(1,2/试题难度)，distinguish(1,2/区分)}

现在我要从题库随机抽出20道题，type：类型1的6道，2的7道，3的7道；difficulty：难度1的8道，2的12道；distinguish：区分1的13道，2的7道：请问能用SQL查询出来吗？

如果能用SQL查询出来，SQL语句该怎么写？

参考解：

create table #t(

id int ,

[type] int,

[difficurity] int,

[distinguish] int);

declare @type1 int

declare @type2 int

declare @type3 int

declare @difficulty1 int

declare @difficulty2 int

declare @distinguish1 int

declare @distinguish2 int

set @type1=1

set @type2=2

set @type3=3

set @difficulty1=1

set @difficulty2=2

set @distinguish1=1

set @distinguish2=2

declare @i int

set @i = 1

while (@i <= 20)

begin

if (select COUNT(*) from #tb where [TYPE]=1) = 6

set @type1 = 0

if (select COUNT(*) from #tb where [TYPE]=2) = 7

set @type2 = 0

if (select COUNT(*) from #tb where [TYPE]=3) = 7

set @type3 = 0

if (select COUNT(*) from #tb where [difficurity]=1) = 8

set @difficulty1=0

if (select COUNT(*) from #tb where [difficurity]=2) = 12

set @difficulty2=0

if (select COUNT(*) from #tb where [distinguish]=1) = 13

set @distinguish1=0

if (select COUNT(*) from #tb where [distinguish]=2) = 7

set @distinguish2=0

insert into #t

select top 1 *

from T_EXAM te

where [TYPE] in (@type1,@type2,@type3)

and [difficurity] in (@difficulty1,@difficulty2)

and [distinguish] in (@distinguish1,@distinguish2)

and not exists(select * from #t t2 where te.[id]=t2.[id])

order by newid()

if @@RowCount = 0 //已没有符合记录

break;

else

set @i = @i + 1

end

select * from #t

（注：它这里的随机主要依靠函数newid()）