SQL您可以在嵌套SELECT的WHERE中使用CASE吗？

Question

我正在尝试将某些记录放入第二个查询的子集中。我一直得到的错误是：“表别名多次使用：Eqanswer - SQL语句中的错误位置是：199（行：3列：22）”这只是最后一条消息，我错过了明显的答案解决它，但我真的想知道这是否有效。

    SELECT 
        e.entityid, e.entitynum, e.entityrole, eq.memotext, eq.fieldnum
    FROM 
        ( SELECT 
            DISTINCT entitynum 
          FROM Eqanswer, entities
                LEFT JOIN Eqanswer 
                    ON (Eqanswer.entitynum = entities.entitynum) 
          WHERE 
                entities.partyID LIKE
                    CASE 
                        WHEN (entities.partyID LIKE '%Joe%' 
                            OR entities.partyID LIKE '%Bob%' 
                            OR entities.partyID LIKE '%Bill%') 
                        THEN
                            (eqanswer.entityrole = 'F_TL' 
                            AND (CONVERT(eqanswer.memotext, sql_date)=curDate() -5 ))
                        ELSE
                            (eqanswer.entityrole = 'F_TL' AND eqanswer.fieldnum = 160 
                            AND (CONVERT(eqanswer.memotext,sql_date) = CurDate() -1 ))
                        END  
        ) AS bs  

        LEFT JOIN Entities e ON (bs.entitynum = e.entitynum)
        LEFT JOIN Eqanswer eq ON (bs.entitynum = eq.entitynum)
    WHERE((eq.entityrole = 'R_CKLIST' AND eq.fieldnum in (8,9,10,11,34,35))
    OR (eq.entityrole = 'F_TL' AND eq.fieldnum in (104,112,158,160))
    OR (eq.entityrole = 'C_REVIEW' AND eq.fieldnum = 69))
    ORDER BY e.entitynum

我尝试了以下两种方法：

    SELECT 
    e.entityid, e.entitynum, e.entityrole, eq.memotext, eq.fieldnum
    FROM ( SELECT 
        DISTINCT entitynum 
            FROM Eqanswer, entities
            LEFT JOIN Eqanswer 
                ON (Eqanswer.entitynum = entities.entitynum) 
      WHERE 
            entities.partyID 
                CASE 
                    WHEN (entities.partyID LIKE '%Joe%' 
                        OR entities.partyID LIKE '%Bob%' 
                        OR entities.partyID LIKE '%Bill%') 
                    THEN
                        (eqanswer.entityrole = 'F_TL' 
                        AND eqanswer.fieldnum = 160
                        AND (CONVERT(eqanswer.memotext, sql_date)=curDate() -5 ))
                    ELSE
                        (eqanswer.entityrole = 'F_TL' AND eqanswer.fieldnum = 160 
                        AND (CONVERT(eqanswer.memotext,sql_date) = CurDate() -1 ))
                    END  
    ) AS bs  

    LEFT JOIN Entities e ON (bs.entitynum = e.entitynum)
    LEFT JOIN Eqanswer eq ON (bs.entitynum = eq.entitynum)
    WHERE((eq.entityrole = 'R_CKLIST' AND eq.fieldnum in (8,9,10,11,34,35))
    OR (eq.entityrole = 'F_TL' AND eq.fieldnum in (104,112,158,160))
    OR (eq.entityrole = 'C_REVIEW' AND eq.fieldnum = 69))
    ORDER BY e.entitynum

和

    SELECT e.entityid, e.entitynum, e.entityrole, e.thestatus, eq.memotext, eq.dateentered, eq.datechgd, eq.fieldnum, e.docloc 
    FROM (SELECT DISTINCT eqanswer.entitynum FROM eqanswer
      LEFT JOIN entities ON (Eqanswer.entitynum = entities.entitynum) 
      WHERE entities.partyID
          CASE WHEN (entities.party3ID LIKE '%Joe%' 
                    OR entities.party3ID LIKE '%Bob%' 
                    OR entities.party3ID LIKE '%Bill%') 
                    THEN
          CASE WHEN  (eqanswer.entityrole = 'F_TL' 
             AND eqanswer.fieldnum = 160 
             AND (CONVERT(eqanswer.memotext, sql_date)=curDate() -5 ))
             THEN 1 ELSE 0 END
          ELSE
          CASE WHEN (eqanswer.entityrole = 'F_TL' 
             AND eqanswer.fieldnum = 160 
             AND (CONVERT(eqanswer.memotext,sql_date) = CurDate() -1 ))
          THEN 1 ELSE 0 END
          END = 1
      ) AS bs  
   LEFT JOIN Entities e ON (bs.entitynum = e.entitynum)
   LEFT JOIN Eqanswer eq ON (bs.entitynum = eq.entitynum)
   WHERE((eq.entityrole = 'R_CKLIST' AND eq.fieldnum in (8,9,10,11,34,35))
   OR (eq.entityrole = 'F_TL' AND eq.fieldnum in (104,112,158,160))
   OR (eq.entityrole = 'C_REVIEW' AND eq.fieldnum = 69))
   ORDER BY e.entitynum

两者都抛出错误，但这就像语法错误（我的错）。

Answer 1

你真的有Eqanswer两次：

FROM Eqanswer, entities
LEFT JOIN Eqanswer 

修改

好的，这个子选择在很多地方都是错误的:(我会将我的评论添加为字符串，而不是评论，以使它们更加突出）

SELECT  entitynum 
FROM Eqanswer, entities
LEFT JOIN Eqanswer             'this is the duplicate table name'
    ON (Eqanswer.entitynum = entities.entitynum) 
WHERE entities.partyID LIKE    
    'LIKE implies that partyID AND the CASE expression are both strings'
    CASE 
        WHEN (entities.partyID LIKE '%Joe%' 
                        OR entities.partyID LIKE '%Bob%' 
                        OR entities.partyID LIKE '%Bill%') 
        THEN (eqanswer.entityrole = 'F_TL' 
             AND (CONVERT(eqanswer.memotext, sql_date)=curDate() -5 ))
             'but THIS is a boolean expression'
        ELSE (eqanswer.entityrole = 'F_TL' 
             AND eqanswer.fieldnum = 160 
             AND (CONVERT(eqanswer.memotext,sql_date) = CurDate() -1 ))
             'and THIS too'
    END  
) AS bs  

因此，LIKE对未知数据类型的列进行操作，而CASE则对布尔表达式进行操作。最有可能的是，行entities.partyID LIKE只是一个复制和粘贴错误（希望如此）。让我们忽略它。

作为CASE子句的结果，您不能返回布尔表达式。因此，您需要重写CASE以返回一个整数，并将此值与您想要的WHERE条件进行比较。

可能是这样的：

WHERE 
    CASE 
        WHEN (entities.partyID LIKE '%Joe%' 
                        OR entities.partyID LIKE '%Bob%' 
                        OR entities.partyID LIKE '%Bill%') 
        THEN
            CASE WHEN  (eqanswer.entityrole = 'F_TL' 
                 AND (CONVERT(eqanswer.memotext, sql_date)=curDate() -5 ))
            THEN 1 ELSE 0 END
        ELSE
            CASE WHEN (eqanswer.entityrole = 'F_TL' 
                 AND eqanswer.fieldnum = 160 
                 AND (CONVERT(eqanswer.memotext,sql_date) = CurDate() -1 ))
            THEN 1 ELSE 0 END
    END = 1

Answer 2

SELECT 
        e.entityid, e.entitynum, e.entityrole, eq.memotext, eq.fieldnum
    FROM 
        ( SELECT 
            DISTINCT entitynum 
         /* THIS NEEDS TO BE CHANGED {Eqanswer} used 2 times without any alias */
          FROM Eqanswer, entities
                LEFT JOIN Eqanswer 
                    ON (Eqanswer.entitynum = entities.entitynum) 
          WHERE 
                entities.partyID LIKE  /* why you need this ?? */
                    CASE 
                        WHEN (entities.partyID LIKE '%Joe%' 
                            OR entities.partyID LIKE '%Bob%' 
                            OR entities.partyID LIKE '%Bill%') 
                        THEN
                            (eqanswer.entityrole = 'F_TL' 
                            AND (CONVERT(eqanswer.memotext, sql_date)=curDate() -5 ))
                        ELSE
                            (eqanswer.entityrole = 'F_TL' AND eqanswer.fieldnum = 160 
                            AND (CONVERT(eqanswer.memotext,sql_date) = CurDate() -1 ))
                        END  
        ) AS bs  

        LEFT JOIN Entities e ON (bs.entitynum = e.entitynum)
        LEFT JOIN Eqanswer eq ON (bs.entitynum = eq.entitynum)
    WHERE((eq.entityrole = 'R_CKLIST' AND eq.fieldnum in (8,9,10,11,34,35))
    OR (eq.entityrole = 'F_TL' AND eq.fieldnum in (104,112,158,160))
    OR (eq.entityrole = 'C_REVIEW' AND eq.fieldnum = 69))
    ORDER BY e.entitynum