Question

我制作子查询时遇到问题

＆＃13;

select r.Request_ID,
(
(select e.ReportsTo, (select e1.FirstName from Employees e1 where e1.NIK = e.ReportsTo) as FirstName, 
(select e1.NIK from Employees e1 where e1.NIK=e.NIK) as Attention, 
(select e1.FirstName from Employees e1 where e1.NIK=e.NIK) as AttentionName 
from Employees e where e.ReportsTo ='CS-NIK-2016-0150' and e.NIK='CS-NIK-2016-0160')
)
from Request r where r.Request_ID='CS-REQ-BDG-201604-10099'

＆＃13;

操作数应包含1列，为什么？

Answer 1

使用join而不是子查询。您的子查询也可能返回超过1行，因此它显示错误。为了避免错误使用限制，每个选择都不是最佳解决方案，因为在这种情况下它将只返回第1行。

select r.Request_ID,
(
(select e.ReportsTo, (select e1.FirstName from Employees e1 where e1.NIK = e.ReportsTo limit 1) as FirstName, 
 e.NIK as Attention, FirstName as AttentionName 
from Employees e where e.ReportsTo ='CS-NIK-2016-0150' and e.NIK='CS-NIK-2016-0160')
)
from Request r where r.Request_ID='CS-REQ-BDG-201604-10099'

操作数应包含1列子查询MySQL

1 个答案: