在动态 where 子句中使用子查询

Question

我正在尝试执行以下操作：

SELECT *
FROM myTable
WHERE workplace IN
    (CASE @param
        WHEN 'a' THEN (SELECT workplace 
                      FROM workPlaceTable
                      WHERE condition1)
        WHEN 'b' THEN (SELECT workplace 
                      FROM workPlaceTable
                      WHERE condition2)
    END)

这将始终 return：

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

有人知道我如何在没有 if 和重复查询的情况下实现这一点吗？

Answer 1

我认为您根本不需要子查询，只需使用带有 WHERE 子句的 JOIN：

SELECT T1.*
FROM myTable T1
INNER JOIN workPlaceTable T2 ON T1.workplace = T2.workplace
WHERE (@param = 'a' AND condition1) OR (@param = 'b' AND condition2)

如果 @param = 'a' 则计算 condition1，否则计算 condition2。

Answer 2

Has anybody an idea how I can realize this without an if and repeating the query?

这样的东西可能适合你。

select *
from myTable
where @Param = 'a' and workplace in (
                                    select workplace 
                                    from workPlaceTable
                                    where condition1
                                    ) or
      @Param = 'b' and workplace in (
                                    select workplace 
                                    from workPlaceTable
                                    where condition2
                                    );

Answer 3

为了详细说明@Allan 的回答，连接看起来像这样：

SELECT myTable.*
FROM myTable
INNER JOIN workPlaceTable ON myTable.workplace = workPlaceTable.workplace AND
(
    (@param = 'a' AND <<condition1>>) OR (@param = 'b' AND <<condition2>>)
)

顺便说一句，这个问题与dynamic-sql无关。

Answer 4

你可以试试这个；


SELECT *
  FROM myTable
 WHERE (@param = 'a' and
       workplace in
       (SELECT workplace FROM workPlaceTable WHERE condition1))
    OR (@param = 'b' and
       workplace in
       (SELECT workplace FROM workPlaceTable WHERE condition2))
</pre>

在动态 where 子句中使用子查询

Using a subquery in a dynamic where clause

tsql

sql-server