tbl_Inv:
no classNo name
I001 C001 aaaa
I002 C001 bbbb
tbl_Inv_Class:
classNo className
C001 消耗品
查询要成这个样子:
no classNo className name
I001 C001 消耗品 aaaa
I002 C001 消耗品 bbbb
原来我是这样写的:
select DISTINCT a.no,a.classno,b.classname,a.name from tbl_Inv a,tbl_Inv_Class b
where a.classNo=b.classNo有没有更正规的写法?不用DISTINCT的
no classNo name
I001 C001 aaaa
I002 C001 bbbb
tbl_Inv_Class:
classNo className
C001 消耗品
查询要成这个样子:
no classNo className name
I001 C001 消耗品 aaaa
I002 C001 消耗品 bbbb
原来我是这样写的:
select DISTINCT a.no,a.classno,b.classname,a.name from tbl_Inv a,tbl_Inv_Class b
where a.classNo=b.classNo有没有更正规的写法?不用DISTINCT的
select a.no,a.classno,b.classname,a.name from tbl_Inv a,tbl_Inv_Class b
where a.classNo=b.classNo
or:
select a.no,a.classno,b.classname,a.name
from tbl_Inv a inner join tbl_Inv_Class b
on a.classNo=b.classNo
如果tbl_Inv的classNo在tbl_Inv_Class可能没有
select a.no,a.classno,b.classname,a.name
from tbl_Inv a left join tbl_Inv_Class b
on a.classNo=b.classNo
from tbl_Inv as a , tbl_Inv_Class as b
where a.classNo = b.classNo
tbl_Inv表里的classNo 可能为空的时候怎么查呢?
select a.no,a.classno,b.classname,a.name
from tbl_Inv a left join tbl_Inv_Class b
on a.classNo=b.classNo
from tbl_Inv as a inner join tbl_Inv_Class as b on a.classNo = b.classNo