Question

我无法理解错误代码。我从客户表中获取客户名称，然后我想从分支表中获取出价的cid，然后我尝试在branches_services表中按出价对branches_services.sid和services.sid进行分组所以我可以找到服务表中的客户服务费大于2000的费用。

select cname from clients where cid in 
(select cid from branches where bid in (select branches_services.sid, services.sid 
from branches_services, services 
where branches_services.sid=services.sid group by bid having sum(sfee) >= 2000));

ERROR 1241（21000）：操作数应包含1列

Answer 1

您的一个子查询返回两列，但您只使用一个值来检查是否在返回的值对中找到它。这里：

....bid in (select branches_services.sid, services.sid 
from branches_services, services ...

因此，假设branches_services表具有列bid，则查询应为：

select cname from clients 
where cid in 
(select cid from branches 
   where bid in 
    (select branches_services.bid from branches_services join services 
     on branches_services.sid=services.sid 
     group by bid
     having sum(sfee)>=2000));

join语句出错

1 个答案: