如何在带有IN子句的WHERE中使用CASE语句？

Question

我试图做以下（伪代码，因为它不编译）：

declare showListedOrSold  int = 1 -- get value from config table

select *
from table
where CASE WHEN @showListedOrSold = 0 THEN id IN (1, 2, 5, 6, 10, 11) 
             WHEN @showListedOrSold = 1 THEN id IN (1, 5, 6, 10, 11) 
             WHEN @showListedOrSold = 2 THEN id IN (2) 
      END

基本上取决于showListedOrSold值，它应该带回某些id值。

声明不喜欢IN子句。 这个用例的正确语法是什么？

Answer 1

如果您想要“优雅的解决方案”，您可能需要考虑将这些值存储在可在查询中使用的表中。

CREATE TABLE #ValidIds(
    ShowListedOrSold int,
    id int);

INSERT INTO #ValidIds
VALUES( 0, 1),
      ( 0, 2),
      ( 0, 5),
      ( 0, 6),
      ( 0, 10),
      ( 0, 11),
      ( 1, 1),
      ( 1, 5),
      ( 1, 6),
      ( 1, 10),
      ( 1, 11),
      ( 2, 2);

SELECT *
FROM table t
JOIN #ValidIds v ON t.id = v.id
AND v.ShowListedOrSold = @ShowListedOrSold;

Answer 2

您可以使用OR而不是CASE来解决此问题：

SELECT *
FROM table
WHERE (@showListedOrSold = 0 AND id IN (1, 2, 5, 6, 10, 11))
        OR (@showListedOrSold = 1 AND id IN (1, 5, 6, 10, 11))
        OR (@showListedOrSold = 2 AND id IN (2))

Answer 3

这开始变得相当复杂。 我可能会推荐一种join方法：

select t.*
from table t join
     (values (0, 1), (0, 2), (0, 5), (0, 6), (0, 10), (0, 11),
             (1, 1), (1, 5), (1, 6), (1, 10), (1, 11),
             (2, 2)
     ) v(slos, id)
     on t.slos = @showListedOrSold and
        v.id = s.id

如果变量为null您可以轻松展开它以显示所有行：

     on (t.slos = @showListedOrSold and
         v.id = s.id
        ) or
        @showListedOrSold is null

Answer 4

案例的工作方式，你必须返回一个值，然后检查值。

declare @showListedOrSold int = 1 -- get value from config table

select  *
from    [table]
where   (case
            when @showListedOrSold = 0 and  id in (1, 2, 5, 6, 10, 11) then 1
            when @showListedOrSold = 1 and  id in (1, 5, 6, 10, 11) then 1
            when @showListedOrSold = 2 and  id in (2) then 1
        else 0
        end) = 1

Answer 5

您可以构造SQL语句然后执行它：

declare  @showListedOrSold Int = 1
Declare @vSQL VarChar(200)

Set @vSQL = 'select * from #tbl where id In '
Set @vSQL = @vSQL + 
                    CASE WHEN @showListedOrSold = 0 THEN '(1, 2, 5, 6, 10, 11)'
                         WHEN @showListedOrSold = 1 THEN '(1, 5, 6, 10, 11)' 
                         WHEN @showListedOrSold = 2 THEN '(2)'
                    END

Execute(@vSQL)

Answer 6

你可以像WHERE子句中的子查询一样给它：

select *
from table
where @showListedOrSold in (select  (CASE WHEN @showListedOrSold = 0 THEN id IN (1, 2, 5, 6, 10, 11) 
             WHEN @showListedOrSold = 1 THEN id IN (1, 5, 6, 10, 11) 
             WHEN @showListedOrSold = 2 THEN id IN (2) 
      END) as ABCD from table)