Sql server 2012 如何将整个SQL查询放入CASE语句中

当我在不使用switch-case的情况下运行时，写在case中的查询运行良好，但当我将此查询放在case中时，它开始出现错误。如何将查询更改为在switch-case中运行

Declare @number int 
set @number = 1


SELECT
    CASE @number
       WHEN 1 THEN (SELECT     
                        userId, checkfreeId, role, buname, fiservEmailId 
                    FROM      
                        (SELECT     
                             tbl_buLogin.userId, tbl_buLogin.checkfreeId,
                             tbl_buroles.role, tbl_bu.buname, 
                             tbl_buLogin.fiservEmailId
                         FROM          
                             tbl_buLogin 
                         INNER JOIN
                             tbl_buroles ON tbl_buLogin.roleId = tbl_buroles.id 
                         INNER JOIN
                             tbl_userbujoin ON tbl_userbujoin.userId = tbl_buLogin.userId 
                         INNER JOIN
                             tbl_bu ON tbl_bu.buid = tbl_userbujoin.buId 
                                    AND tbl_bu.buid IN (SELECT tbl_userbujoin.buId 
                                                        FROM tbl_buLogin
                                                        INNER JOIN tbl_userbujoin ON tbl_buLogin.userId = tbl_userbujoin.userId
                                                        WHERE tbl_buLogin.checkfreeId = 'testiso')
                         UNION
                         SELECT     
                             tbl_buLogin_2.userId, tbl_buLogin_2.checkfreeId, tbl_buroles_1.role, tbl_bu_1.buname, tbl_buLogin_2.fiservEmailId
                         FROM         
                             tbl_buLogin AS tbl_buLogin_2 
                         INNER JOIN
                             tbl_buroles AS tbl_buroles_1 ON tbl_buLogin_2.roleId = tbl_buroles_1.id 
                         INNER JOIN
                             tbl_bu AS tbl_bu_1 ON tbl_bu_1.buid = tbl_buLogin_2.buId 
                                                AND tbl_bu_1.buid IN (SELECT tbl_userbujoin.buId 
                                                                      FROM tbl_buLogin
                                                                      INNER JOIN 
                                                                          tbl_userbujoin on tbl_buLogin.userId = tbl_userbujoin.userId
                                                                      WHERE tbl_buLogin.checkfreeId = 'testiso')

                         WHERE     
                             (tbl_buLogin_2.userId NOT IN (SELECT     tbl_userbujoin_1.userId
                                                           FROM tbl_buLogin AS tbl_buLogin_1
                                                           INNER JOIN tbl_userbujoin AS tbl_userbujoin_1 ON tbl_userbujoin_1.userId = tbl_buLogin_1.userId))) AS tbl 
                ORDER BY role)
        ELSE 'NO'
    END

---

为什么不使用

IF-ELSE

IF @number = 1 THEN
BEGIN 
  --your Query here
END
ELSE
  SELECT 'NO'

---

非常混乱的帖子，我建议IF/ELSE IF-CASE不是用来控制流的。T-SQL中的

CASE

是一个表达式（比如

a+b

）-不是一个语句

CASE

最终将返回一个单一的原子值-它不是为交替执行一组或另一组代码而设计的