多表查询
有20个表，数据类型，结构完全相同
a01 产品名称，数量
b01 产品名称，数量
c01 产品名称，数量
d01 产品名称，数量
.
.
.

想要用语句实现每个表的累计数量
a01 b01 c01 d01
1000 500 3000 444




[解决办法]
declare @tab varchar(20)
set @tab= '表名 '
print( 'select sum(case when col1= ' 'a01 ' ' then col3 else 0 end)a01,
sum(case when col1= ' 'a01 ' ' then col3 else 0 end)b01,
sum(case when col1= ' 'a01 ' ' then col3 else 0 end)c01,
sum(case when col1= ' 'a01 ' ' then col3 else 0 end)d01
from '+@tab+ ' group by col1 ')
[解决办法]
select
(select Sum(数量) as a01 from a01)a
Cross join
(select Sum(数量) as b01 from b01)b
Cross join
(select Sum(数量) as c01 from c01)c
Cross join
(select Sum(数量) as d01 from d01)d