帮忙解释一下,这个SQL语句

[apple18]

DECLARE @SQL AS VARCHAR(8000)

set @sql = ' select '
select @sql = @sql + 'sum(case NDATE when '''+NDATE+'''
then KVOL else 0 end) as ''日期'+NDATE+''','
from (SELECT DISTINCT NDATE FROM p WHERE NDATE>='20061009' AND NDATE<='20061013') as a

select @sql = left(@sql,len(@sql)-1) +' FROM p WHERE NDATE>=''20061009'' AND NDATE<=''20061013'' '


PRINT @sql
EXEC (@SQL)

[guyan033]

行列互换

把各时间换为列

[子陌红尘]

PRINT @sql --这一句输出了拼接完的SQL语句

[happydreamer]

--example
字段：客户名称 bb je
a1 HKD 100
a1 HKD 200
a1 USD 150
a1 USD 250
a2 HKD 200
a2 USD 100
a3 HKD 300
a3 HKD 400

先对a分组,再分别合计b=h和b=u的数放在sumhk,sumus字段中

结果：客户名称 港币 美金
a1 300 400
a2 200 100
a3 700 0
Answer:
select 客户名称,
sum(case when bb='HKD' then je else 0 end) as 港币,
sum(case when bb='USD' then je else 0 end) as 美金
from data group by 客户名称

--一样的效果,用了动态sql

declare @sql varchar(8000)
set @sql = 'select 客户名称'
select @sql = @sql + ',sum(case bb when '''+bb+''' then je end) ['+bb+']'
from (select distinct bb from data) as a
select @sql = @sql+' from data group by 客户名称'
exec(@sql)

[lxzm1001]

小黑子是吧

[apple18]

select @sql = @sql + ',sum(case bb when '''+bb+''' then je end) ['+bb+']'
from (select distinct bb from data) as a
实现动态效果，
但怎么解释啊，有相关的语法说明吗

[xyxfly]

select @sql = @sql + ',sum(case bb when '''+bb+''' then je end) ['+bb+']'
from (select distinct bb from data) as a

这里相当于一个循环

其实你可以把print出来的语句看看就知道了 :)

[hhhdyj]

这样理解：
从下面的结果集一行一行的取数据，然后按上面语句连接
SELECT DISTINCT NDATE FROM p WHERE NDATE>='20061009' AND NDATE<='20061013'