Question

我想要做的是使用case-when将多行转换为单行，但我得到

ORA-00979：不是GROUP BY表达式

这是我的查询

SELECT  P.APPDISPLAYNAME AS PLAYERNAME ,
        CASE WHEN GS.SETNUMBER = 1 THEN SS.SETSCORE END AS set1,
        CASE WHEN GS.SETNUMBER = 2 THEN SS.SETSCORE END AS set2,
        CASE WHEN GS.SETNUMBER = 3 THEN SS.SETSCORE END AS set3,
        CASE WHEN GS.SETNUMBER = 4 THEN SS.SETSCORE END AS set4
FROM    TENNISMATCH TM ,
        TEAM T ,
        TEAMPLAYER TP ,
        TOURNAMENTPLAYER TRP ,
        PLAYER P ,
        SETSCORE SS ,
        GAMESET GS ,
        PLAYERBIO PB
WHERE   TM.EVENTTYPE = 'MEN_SINGLES'
        AND TM.MATCHSTATUS = 'LIVE'
        AND TM.TENNISMATCHID = T.TENNISMATCHID
        AND T.TEAMID = TP.TEAMID
        AND TP.TOURNAMENTPLAYERID = TRP.TOURNAMENTPLAYERID
        AND TRP.PLAYERID = P.PLAYERID
        AND T.TEAMID = SS.TEAMID
        AND SS.GAMESETID = GS.GAMESETID
        AND P.PLAYERID = PB.PLAYERID
GROUP BY P.APPDISPLAYNAME

Answer 1

SELECT子句中显示的所有列都必须包含在您的GROUP BY子句中，或者应用某种Aggregate function。

在您的情况下，如果您只想返回一行，则应该使用MAX()函数应用于每个CASE结果。

如果CASE语句可以为每一行返回不同的结果，那么这当然不准确。但如果是这样的话，那么你的问题就无法解决了。

尝试将其添加到每个CASE：

MAX(CASE WHEN GS.SETNUMBER=1 THEN SS.SETSCORE END) as set1

Answer 2

您必须将SELECT的所有列放在GROUP BY中，或使用汇总函数将结果压缩为单个值（例如MIN，MAX或SUM）。

Answer 3

首先，您应该学会使用正确的显式JOIN语法。甚至Oracle现在也建议使用它。

其次，您的SELECT需要聚合功能。我会推荐这样的东西：

SELECT  P.APPDISPLAYNAME AS PLAYERNAME ,
        MAX(CASE WHEN GS.SETNUMBER = 1 THEN SS.SETSCORE END) AS set1,
        MAX(CASE WHEN GS.SETNUMBER = 2 THEN SS.SETSCORE END) AS set2,
        MAX(CASE WHEN GS.SETNUMBER = 3 THEN SS.SETSCORE END) AS set3,
        MAX(CASE WHEN GS.SETNUMBER = 4 THEN SS.SETSCORE END) AS set4
. . .

使用Case-When在SQL中将多行转换为单行

3 个答案: