类型表里的名称,在另外一个表里有这个表的名称,但可以为空,现在我要根据类型表的名称查询另一个表的数量
select roomtype.roomtypename,count(client.clientname)
from roomtype inner join client on roomtype.roomtypename like client.needroomtype
group by roomtype.roomtypename使用这样查,但查出来有问题,会比原来的数据多几条
现在怎么查
select roomtype.roomtypename,count(client.clientname)
from roomtype inner join client on roomtype.roomtypename like client.needroomtype
group by roomtype.roomtypename使用这样查,但查出来有问题,会比原来的数据多几条
现在怎么查
select roomtype.roomtypename,count(client.clientname)
from roomtype inner join client on roomtype.roomtypename = client.needroomtype
group by roomtype.roomtypename
from roomtype left join client on roomtype.roomtypename =client.needroomtype
group by roomtype.roomtypename不知道,是否你要的
a.roomtypename,
COUNT(DISTINCT b.clientname) --描述不清楚,仅做参考
FROM
roomtype a
INNER JOIN client b
ON a.roomtypename LIKE b.needroomtype --用like相当于:ON a.roomtypename = b.needroomtype
GROUP BY
a.roomtypename