Mysql 不满足条件的选择查询返回值0
我试图选择Mysql 不满足条件的选择查询返回值0,mysql,Mysql,我试图选择count(*)作为变量,根据某些条件按产品分组 如果不满足该条件,我希望查询返回0作为该乘积的count变量值 我正在使用MySQL数据库并尝试在SAS中使用它,以下是我的查询: SELECT COUNT(*) AS common_mtrl, product AS product2 FROM join_mkt_sort A, support_mtrl B WHERE support_mtrl_ind >= 1 AND A.EKEY =
count(*)
作为变量,根据某些条件按产品分组
如果不满足该条件,我希望查询返回0作为该乘积的count变量值
我正在使用MySQL数据库并尝试在SAS中使用它,以下是我的查询:
SELECT COUNT(*) AS common_mtrl, product AS product2
FROM join_mkt_sort A, support_mtrl B
WHERE support_mtrl_ind >= 1
AND A.EKEY = B.SKEY
AND A.PKEY = B.SKEY
GROUP BY product
我希望查询为不符合条件的产品将
0
分配给变量common\u mtrl
。问题在于您的加入。假设您想要的所有行都在“A”表中,您可以这样连接它们:
select count(B.SKEY) as common_mtrl, product as product2
from join_mkt_sort A left outer join
support_mtrl B
on A.EKEY = B.SKEY and A.PKEY = B.SKEY and
support_mtrl_ind >=1
group by product;
左侧外部联接
保留第一个表中的所有行,即使没有匹配项。count()
统计匹配数。如果count为0,则检查条件
select sum(case when support_mtrl_ind >=1 then 1 else 0 end) as common_mtrl,
product as product2
from join_mkt_sort A
,support_mtrl B
where A.EKEY = B.SKEY and A.PKEY = B.SKEY
group by product
set @count int=0 set @result int select @count=count(*) as
common_mtrl,product as product2 from join_mkt_sort A,support_mtrl B
where support_mtrl_ind >=1
and A.EKEY = B.SKEY and A.PKEY = B.SKEY
group by product if(@count=0) set @result=0
product
在哪个表上?您是否有一个表格来记录所有产品的详细信息?您担心产品不令人满意的“条件”是什么?join或support\u mtrl\u ind>=1?Gordon的答案对我很有用。@user2542275那么别忘了将其标记为正确答案。他没有具体说明他担心满足的“条件”。如果连接是他的条件,那么您的答案将处理该情况。如果support\u mtrl\u ind>=1是他的情况,我的人会处理这个案子。@BillGregg。这可以同时处理这两个问题。比较在on
子句中,因此将聚合A
中的所有行。
set @count int=0 set @result int select @count=count(*) as
common_mtrl,product as product2 from join_mkt_sort A,support_mtrl B
where support_mtrl_ind >=1
and A.EKEY = B.SKEY and A.PKEY = B.SKEY
group by product if(@count=0) set @result=0