Question

我现在被卡住了......

我有4种类型的发票需要不同的选定字段......

现在我正在尝试类似......

SELECT 
    CASE WHEN EXISTS (SELECT * FROM invoices WHERE type ='inv') THEN
            (SELECT a,b,c FROM invoices)

WHEN EXISTS (SELECT * FROM invoices WHERE type ='credit') THEN
            (SELECT d,e,f FROM invoices)
end
from invoices

这无法正常工作......

我得到了：

Msg 116，Level 16，State 1，Line 6
当未使用EXISTS引入子查询时，只能在选择列表中指定一个表达式。

有没有人知道如何处理这样的事情？我完全失去了......

Answer 1

由于CASE WHEN指令，您不能放置子查询。试试，其中之一：

SELECT  case [type]
            when 'inv'    then a
            when 'credit' then d        
            else 0
        end
        ,
        case [type]
            when 'inv'    then b
            when 'credit' then e        
            else 0
        end
        ,
        case [type]
            when 'inv'    then c
            when 'credit' then f
            else 0
        end
from invoices

或

select  a, b, c
from    invoices
where   [type] = 'inv'
union
select  d, e, f
from    invoices
where   [type] = 'credit'

Answer 2

我认为这是你想要的，当type ='inv'时列a，b和c，或者当type ='credit'时列d，e，f：

SELECT a,b,c FROM invoices WHERE type ='inv'
UNION ALL
SELECT d,e,f FROM invoices WHERE type ='credit'

Answer 3

您还可以返回忽略所有字段或将记录的无效字段设置为空。

SELECT 
    a=CASE WHEN Type='inv' THEN a ELSE NULL END,
    b=CASE WHEN Type='inv' THEN b ELSE NULL END,
    c=CASE WHEN Type='inv' THEN c ELSE NULL END,
    d=CASE WHEN Type='credit' THEN d ELSE NULL END,
    e=CASE WHEN Type='credit' THEN e ELSE NULL END,
    f=CASE WHEN Type='credit' THEN f ELSE NULL END,
FROM
    invoices

Answer 4

尝试这样：

IF EXISTS (SELECT * FROM invoices WHERE type ='inv')
            (SELECT a,b,c FROM invoices)

ELSE IF EXISTS (SELECT * FROM invoices WHERE type ='credit')
            (SELECT d,e,f FROM invoices)

SQL Server问题中的子查询

4 个答案: