经常用到的交叉表问题 一般用动态SQL能生成动态列

原始表如下格式：

Class	CallDate	CallCount
1	2005-8-8	40
1	2005-8-7	6
2	2005-8-8	77
3	2005-8-9	33
3	2005-8-8	9
3	2005-8-7	21

根据Class的值，按日期分别统计出CallCount1，CallCount2，CallCount3。当该日期无记录时值为0，
要求合并成如下格式：

CallDate	CallCount1	CallCount2	CallCount3
2005-8-9	0	0	33
2005-8-8	40	77	9
2005-8-7	6	0	21

创建测试环境：


Create table T (Class varchar(2),CallDate datetime, CallCount int)


insert into T select '1','2005-8-8',40


union all select '1','2005-8-7',6


union all select '2','2005-8-8',77


union all select '3','2005-8-9',33


union all select '3','2005-8-8',9


union all select '3','2005-8-7',21

动态SQL


declare @s varchar(8000)


set @s='select CallDate '


select @s=@s+',[CallCount'+Class+']=sum(case when Class='''+Class+''' then CallCount else 0 end)'


from T


group by Class


set @s=@s+' from T group by CallDate order by CallDate desc '


exec(@s)

结果

CallDate	CallCount1	CallCount2	CallCount3
2005-08-09 00:00:00.000	0	0	33
2005-08-08 00:00:00.000	40	77	9
2005-08-07 00:00:00.000	6	0	21

删除测试环境
drop table T