如何在单个SQL CASE语句中获取多个列？

Question

我试图从单个CASE语句中获取多个列(在这种情况下为insuredcode,insuredname).

已尝试以下查询,但它将insuredcode和insuredname连接为一列.

从这样的CASE语句中返回两列的正确语法是什么？

select
    case
        when a.policyno[2] in ('E', 'W') then c.insuredcode || c.insuredname
        else b.insuredcode || b.insuredname
    end
from prpcmain a
left join prpcinsured_1 b on b.proposalno=a.proposalno 
left join prpcinsured_2 c on c.proposalno=a.proposalno
where a.policyno in (select policyno from policyno_t);

Answer 1

一个CASE声明只能返回单列没有多列

您需要两个不同的CASE语句才能执行此操作

select
    case
        when a.policyno[2] in ('E', 'W') then c.insuredcode 
        else b.insuredcode 
    end as insuredcode ,
    case
        when a.policyno[2] in ('E', 'W') then  c.insuredname
        else b.insuredname
    end as insuredname
from prpcmain a
left join prpcinsured_1 b on b.proposalno=a.proposalno 
left join prpcinsured_2 c on c.proposalno=a.proposalno
where a.policyno in (select policyno from policyno_t);

Answer 2

它就像任何语言中的 if/else 条件一样，你可以在When语句中定义你的条件，如果条件为 true，SQL 执行Then语句，否则执行Else部分，如下所述：

     Select 
                 CASE 
                    WHEN (cs.ResultSubmitToHOD = 1) THEN 'HOD'
                    WHEN (cs.ResultSubmitToExamDep = 1) THEN 'Exam'
                    ELSE 'Teacher'
                END AS ResultSubmitStatus
     From dbo.CourseSection as cs