SQL Server 2008 中“WHERE”子句中的“CASE”语句答案

【问题标题】："CASE" statement within "WHERE" clause in SQL Server 2008SQL Server 2008 中“WHERE”子句中的“CASE”语句
【发布时间】：2012-01-09 07:36:51
【问题描述】：

我正在处理一个在“WHERE”子句中包含“CASE”语句的查询。但是 SQL Server 2008 在执行时会出现一些错误。谁能帮我正确查询？这是查询：

SELECT
    tl.storenum 'Store #', 
    co.ccnum 'FuelFirst Card #', 
    co.dtentered 'Date Entered',
    CASE st.reasonid 
        WHEN 1 THEN 'Active' 
   WHEN 2 THEN 'Not Active' 
   WHEN 0 THEN st.ccstatustypename 
   ELSE 'Unknown' 
    END 'Status',
    CASE st.ccstatustypename 
        WHEN 'Active' THEN ' ' 
   WHEN 'Not Active' THEN ' ' 
   ELSE st.ccstatustypename 
    END 'Reason',
    UPPER(REPLACE(REPLACE(co.personentered,'RT\\\\',''),'RACETRAC\\\\','')) 'Person Entered',
    co.comments 'Comments or Notes'
FROM 
    comments co
    INNER JOIN cards cc ON co.ccnum=cc.ccnum
    INNER JOIN customerinfo ci ON cc.customerinfoid=ci.customerinfoid
    INNER JOIN ccstatustype st ON st.ccstatustypeid=cc.ccstatustypeid
    INNER JOIN customerstatus cs ON cs.customerstatuscd=ci.customerstatuscd
    INNER JOIN transactionlog tl ON tl.transactionlogid=co.transactionlogid
    LEFT JOIN stores s ON s.StoreNum = tl.StoreNum
WHERE 
    CASE LEN('TestPerson')
        WHEN 0 THEN co.personentered  = co.personentered
   ELSE co.personentered LIKE '%TestPerson'
    END 
    AND cc.ccnum = CASE LEN('TestFFNum')
        WHEN 0 THEN cc.ccnum 
   ELSE 'TestFFNum' 
    END 
    AND CASE LEN('2011-01-09 11:56:29.327') 
        WHEN 0 THEN co.DTEntered = co.DTEntered 
   ELSE 
       CASE LEN('2012-01-09 11:56:29.327') 
           WHEN 0 THEN co.DTEntered >= '2011-01-09 11:56:29.327' 
      ELSE co.DTEntered BETWEEN '2011-01-09 11:56:29.327' AND '2012-01-09 11:56:29.327' 
       END 
    END
    AND tl.storenum < 699 
ORDER BY tl.StoreNum

【问题讨论】：

Case expression, not statement...（case 表达式返回一个值。case 语句用于存储过程中，用于有条件地执行代码。）

标签： sql sql-server case

【解决方案1】：

首先，CASE 语句必须是表达式的部分，而不是表达式本身。

换句话说，您可以：

WHERE co.DTEntered = CASE 
                          WHEN LEN('blah') = 0 
                               THEN co.DTEntered 
                          ELSE '2011-01-01' 
                     END

但它不会像你写的那样工作，例如：

WHERE 
    CASE LEN('TestPerson')
        WHEN 0 THEN co.personentered  = co.personentered
   ELSE co.personentered LIKE '%TestPerson'
    END

使用这样的组合 OR 语句可能会更好：

WHERE (
        (LEN('TestPerson') = 0 
             AND co.personentered = co.personentered
        ) 
        OR 
        (LEN('TestPerson') <> 0 
             AND co.personentered LIKE '%TestPerson')
      )

不过，无论哪种方式，我都不确定您会获得多棒的查询计划。 WHERE 子句中的这些类型的恶作剧通常会阻止查询优化器使用索引。

【讨论】：

WHEN 0 THEN co.personentered = co.personentered，这里不需要这个检查 co.personentered = co.personentered，因为它总是返回 true 并且长度值总是正的。因此，使 LEN('TestPerson') > 0 将减少需要比较的范围
如何在选项 1 和 2 中检查 co.personentered 不为空。现在第 3 个选项就足够了。但我想知道……！！
到目前为止我尝试过where case c when 1 then (DescriptionCode is null) else descriptioncode is not null end，但我显示的错误类似于Incorrect syntax near the keyword 'is'.

【解决方案2】：

尝试以下方法：

SELECT * FROM emp_master 
WHERE emp_last_name= 
CASE emp_first_name 
 WHEN 'test'    THEN 'test' 
 WHEN 'Mr name' THEN 'name'
END

【讨论】：

【解决方案3】：

这应该可以暂时解决您的问题，但我必须提醒您这不是一个好方法：

WHERE 
            CASE LEN('TestPerson')
                WHEN 0 THEN 
                        CASE WHEN co.personentered  = co.personentered THEN 1 ELSE 0 END
                ELSE 
                        CASE WHEN co.personentered LIKE '%TestPerson' THEN 1 ELSE 0 END
            END = 1
        AND cc.ccnum = CASE LEN('TestFFNum')
                            WHEN 0 THEN cc.ccnum 
                            ELSE 'TestFFNum' 
                       END 
        AND CASE LEN('2011-01-09 11:56:29.327') 
                WHEN 0 THEN CASE WHEN co.DTEntered = co.DTEntered THEN 1 ELSE 0 END 
                ELSE 
                    CASE LEN('2012-01-09 11:56:29.327') 
                        WHEN 0 THEN 
                            CASE WHEN co.DTEntered >= '2011-01-09 11:56:29.327' THEN 1 ELSE 0 END 
                        ELSE 
                            CASE WHEN co.DTEntered BETWEEN '2011-01-09 11:56:29.327' 
                                                        AND '2012-01-09 11:56:29.327' 
                                                     THEN 1 ELSE 0 END
                    END
            END = 1
        AND tl.storenum < 699

【讨论】：

【解决方案4】：

我认为您的查询的开头应该是这样的：

SELECT
    tl.storenum [Store #], 
    co.ccnum [FuelFirst Card #], 
    co.dtentered [Date Entered],
    CASE st.reasonid 
        WHEN 1 THEN 'Active' 
        WHEN 2 THEN 'Not Active' 
        WHEN 0 THEN st.ccstatustypename 
        ELSE 'Unknown' 
    END [Status],
    CASE st.ccstatustypename 
        WHEN 'Active' THEN ' ' 
        WHEN 'Not Active' THEN ' ' 
        ELSE st.ccstatustypename 
        END [Reason],
    UPPER(REPLACE(REPLACE(co.personentered,'RT\\\\',''),'RACETRAC\\\\','')) [Person Entered],
    co.comments [Comments or Notes]
FROM comments co
    INNER JOIN cards cc ON co.ccnum=cc.ccnum
    INNER JOIN customerinfo ci ON cc.customerinfoid=ci.customerinfoid
    INNER JOIN ccstatustype st ON st.ccstatustypeid=cc.ccstatustypeid
    INNER JOIN customerstatus cs ON cs.customerstatuscd=ci.customerstatuscd
    INNER JOIN transactionlog tl ON tl.transactionlogid=co.transactionlogid
    LEFT JOIN stores s ON s.StoreNum = tl.StoreNum
WHERE 
    CASE 
      WHEN (LEN([TestPerson]) = 0 AND co.personentered  = co.personentered) OR (LEN([TestPerson]) <> 0 AND co.personentered LIKE '%'+TestPerson) THEN 1
      ELSE 0
      END = 1
    AND

但是

尾巴里的东西完全看不懂

【讨论】：

【解决方案5】：

WHERE 部分可以这样写：

WHERE 
 (LEN('TestPerson') <> 0 OR co.personentered  = co.personentered) AND
 (LEN('TestPerson') = 0 OR co.personentered LIKE '%TestPerson') AND
 (cc.ccnum = CASE LEN('TestFFNum')
                WHEN 0 THEN cc.ccnum 
                ELSE 'TestFFNum' 
              END ) AND
 (LEN('2011-01-09 11:56:29.327') <> 0 OR co.DTEntered = co.DTEntered ) AND
 ((LEN('2011-01-09 11:56:29.327') = 0 AND LEN('2012-01-09 11:56:29.327') <> 0) OR co.DTEntered >= '2011-01-09 11:56:29.327'  ) AND
 ((LEN('2011-01-09 11:56:29.327') = 0 AND LEN('2012-01-09 11:56:29.327') = 0) OR co.DTEntered BETWEEN '2011-01-09 11:56:29.327' AND '2012-01-09 11:56:29.327'  ) AND 
 tl.storenum < 699

【讨论】：

【解决方案6】：

感谢这个问题，实际上我正在寻找以下查询中的其他内容。这可能对某人有所帮助。

      SELECT DISTINCT CASE WHEN OPPORTUNITY='' THEN '(BLANK)' ELSE OPPORTUNITY END
  AS OPP,LEN(OPPORTUNITY) FROM [DBO].[TBL]

上面的查询是填写下拉列表，其中空白值显示为“（空白）”。此外，如果我们将此值传递给 sql where 子句以获取具有其他值的空白值，我不知道如何处理。最后提出了以下解决方案，这可能对某人有所帮助。

来了，

 DECLARE @OPP TABLE (OPP VARCHAR(100))
  INSERT INTO @OPP VALUES('(BLANK)'),('UNFUNDED'),('FUNDED/NOT COMMITTED')
SELECT DISTINCT [OPPORTUNITY]
FROM [DBO].[TBL]   WHERE    (  CASE WHEN   OPPORTUNITY ='' THEN '(BLANK)' ELSE OPPORTUNITY END IN (SELECT OPP FROM @OPP))
ORDER BY 1

【讨论】：

【解决方案7】：

 select 
d.DISTNAME,e.BLKNAME,a.childid,a.studyingclass 
from Tbl_AdmissionRegister a
inner join District_master b on a.Schooid=b.Schooid
where 
case when len('3601')=4   then c.distcd 
           when len('3601')=6   then c.blkcd  
           when len('3601')=11  then c.schcd   end = '3601'

【讨论】：

请提供更多信息，说明您的回答为何有助于解决原始问题。对于有同样问题的用户来说，只发布代码可能有点模糊。

【解决方案8】：

您也可以尝试如下所示。仅显示出境货件

   SELECT shp_awb_no,shpr_ctry_cd, recvr_ctry_cd,
     CASE WHEN shpr_ctry_cd = record_ctry_cd 
     THEN "O" 
     ELSE "I" 
      END AS route
     FROM shipment_details
    WHERE record_ctry_cd = "JP"
      AND "O" = CASE WHEN shpr_ctry_cd = record_ctry_cd 
                THEN "O" 
                ELSE "I" 
                 END

【讨论】：

【解决方案9】：

这是我的解决方案

AND CLI.PE_NOM Like '%' + ISNULL(@NomClient, CLI.PE_NOM) + '%'

问候戴维

【讨论】：

【解决方案10】：

这行得通

declare @v int=A
select * from Table_Name where XYZ=202 
and 
dbkey=(case @v  when A then 'Some Value 1'
else 'Some Value 2'
end)

【讨论】：

【解决方案11】：

CASE LEN('TestPerson')
    WHEN 0 THEN co.personentered  = co.personentered ELSE co.personentered LIKE '%TestPerson'

尝试以下方法：

... and ( 
    (LEN('TestPerson') = 0 and co.personentered  = co.personentered) or
    (LEN('TestPerson') <> 0 and co.personentered LIKE '%TestPerson') ) and ...

【讨论】：

【解决方案12】：

select TUM1.userid,TUM1.first_name + ' ' +TUM1.last_name as NAME,tum1.Business_Title,TUM1.manager_id,tum2.First_Name + ' ' + tum2.Last_Name as [MANAGER NAME],TUM1.project,TUM1.project_code,TUM1.rcc_code,TUM1.department,TCM.Company_Name,
case 
when tum1.Gender_ID=1 then 'male' 
else 'female' 
end 'GENDER'
,tum1.Band as BAND,
case when tum1.Inactive=0 then 'STILL IN COMPANY'
else 'LEFT COMPANY' 
end 'ACTIVE/INACTIVE'
from tbl_user_master TUM1
join tbl_Company_Master TCM on TCM.Company_Code=TUM1.Company_Code 
join tbl_User_Master TUM2 on TUM1.Manager_ID=TUM2.UserID 
where tum1.UserID in ('54545414')

【讨论】：

【解决方案13】：

SELECT * from TABLE 
              WHERE 1 = CASE when TABLE.col = 100 then 1 
                     when TABLE.col = 200 then 2 else 3 END 
                  and TABLE.col2 = 'myname';

这样使用。

【讨论】：