ORACLE SQL 中的 MAX()答案

【问题标题】：MAX() in ORACLE SQLORACLE SQL 中的 MAX()
【发布时间】：2016-11-19 04:30:16
【问题描述】：

我有一个表，其中存储了已完成的维护任务的记录列表以及完成的日期和时间。我正在尝试进行子查询以提取具有最近日期的每个任务的记录。我的 SQL 语句是：

    SELECT "ENGINEERING_COMPLIANCE"."EO" AS "EO",
       "ENGINEERING_COMPLIANCE"."AC" AS "AC",
       "ENGINEERING_COMPLIANCE"."PN" AS "PN",
       "ENGINEERING_COMPLIANCE"."PN_SN" AS "PN_SN",
       "ENGINEERING_COMPLIANCE"."HOURS_RESET" AS "HOURS_RESET",
       "ENGINEERING_COMPLIANCE"."MINUTES_RESET" AS "MINUTES_RESET",
       "ENGINEERING_COMPLIANCE"."CYCLES_RESET" AS "CYCLES_RESET",
       "ENGINEERING_COMPLIANCE"."RESET_DATE" AS "RESET_DATE",
       "ENGINEERING_COMPLIANCE"."RESET_HOUR" AS "RESET_HOUR",
       "ENGINEERING_COMPLIANCE"."RESET_MINUTE" AS "RESET_MINUTE",
       MAX ( "ENGINEERING_COMPLIANCE"."RESET_DATE" ) AS "LAST_COMP_DATE"
  FROM ENGINEERING_COMPLIANCE
GROUP BY ( "ENGINEERING_COMPLIANCE"."EO" ) ,
       ( "ENGINEERING_COMPLIANCE"."AC" ) ,
       ( "ENGINEERING_COMPLIANCE"."PN" ) ,
       ( "ENGINEERING_COMPLIANCE"."PN_SN" )

但是我不断收到以下错误：“ORA-00979: not a GROUP BY expression”

当我删除“GROUP BY”时，我得到： "ORA-00937: 不是单组群函数"

1 - 这究竟是什么意思 2 - 声明有什么问题？

【问题讨论】：

stackoverflow.com/…
4 票赞成一个可以通过谷歌搜索轻松回答的问题？ SO 确实有一个有趣的动态。
ORA-00979 not a group by expression的可能重复
这个问题可能是重复的，但没有说明我可以将它们应用于我的问题的地方。对不起，谢谢你

标签： sql oracle oracle11g max

【解决方案1】：

您在没有聚合函数的情况下在 SELECT 子句中添加的列应该在 GROUP BY 子句中。

为了清楚一点：
举个例子：

您的 SELECT 子句中有 TransactionID、AccountID、TransactionAmount、TransactionDate，并且在所有日期都需要 SUM(TransactionAmount)，在这种情况下，如果您添加

SELECT TransactionDate, TransactionID, AccountID, SUM(TransactionAmount) 
FROM Table 
GROUP BY TransactionDate

然后你会得到一个错误，为什么是因为
假设您在 20160101 上有 4 笔交易，每笔交易金额为 $1000
您的预期结果将是

TransDate      TransAmt
 20140101          4000

在这种情况下，如果在 SELECT 子句中带上其他属性，例如 AccountID 和 TransactionID，它们会去哪里？这就是为什么我们必须在 SELECT 子句中包含 GROUP 子句中的所有属性，除了带有 AGGREGATE 函数的属性。

【讨论】：

谢谢 - 我不再收到错误消息 - 但是我也没有得到最近的日期。是因为我要求列出的其他信息还是我遗漏了什么？我取出了“Reset_Date”，因为那是 MAX 子句中的内容，但现在我又被卡住了。感谢您在此方面的帮助
你还卡住了吗？
是的，我是。我只需要每个项目的最新日期，但我得到了所有日期。 :(
您能否从您的选择和分组依据中删除重置日期、重置小时和重置分钟。你为什么使用重置日期和最大值（重置日期）？？？

【解决方案2】：

我根本不了解 MySQL，但是，在 Oracle 中，您需要按 all 选择列表中列出的非聚合函数列进行分组。

这样的事情应该可以工作：

 SELECT "engineering_compliance"."eo"               AS "EO", 
       "engineering_compliance"."ac"               AS "AC", 
       "engineering_compliance"."pn"               AS "PN", 
       "engineering_compliance"."pn_sn"            AS "PN_SN", 
       "engineering_compliance"."hours_reset"      AS "HOURS_RESET", 
       "engineering_compliance"."minutes_reset"    AS "MINUTES_RESET", 
       "engineering_compliance"."cycles_reset"     AS "CYCLES_RESET", 
       "engineering_compliance"."reset_date"       AS "RESET_DATE", 
       "engineering_compliance"."reset_hour"       AS "RESET_HOUR", 
       "engineering_compliance"."reset_minute"     AS "RESET_MINUTE", 
       Max ("engineering_compliance"."reset_date") AS "LAST_COMP_DATE" 
FROM   engineering_compliance 
GROUP  BY "engineering_compliance"."eo", 
          "engineering_compliance"."ac", 
          "engineering_compliance"."pn", 
          "engineering_compliance"."pn_sn", 
          "engineering_compliance"."hours_reset", 
          "engineering_compliance"."minutes_reset", 
          "engineering_compliance"."cycles_reset", 
          "engineering_compliance"."reset_date", 
          "engineering_compliance"."reset_hour", 
          "engineering_compliance"."reset_minute";

【讨论】：

【解决方案3】：

您必须将 SELECT 的所有列放在 GROUP BY 中

【讨论】：

【解决方案4】：

你应该设置分组中的所有列

 SELECT "ENGINEERING_COMPLIANCE"."EO" AS "EO",
   "ENGINEERING_COMPLIANCE"."AC" AS "AC",
   "ENGINEERING_COMPLIANCE"."PN" AS "PN",
   "ENGINEERING_COMPLIANCE"."PN_SN" AS "PN_SN",
   "ENGINEERING_COMPLIANCE"."HOURS_RESET" AS "HOURS_RESET",
   "ENGINEERING_COMPLIANCE"."MINUTES_RESET" AS "MINUTES_RESET",
   "ENGINEERING_COMPLIANCE"."CYCLES_RESET" AS "CYCLES_RESET",
   "ENGINEERING_COMPLIANCE"."RESET_DATE" AS "RESET_DATE",
   "ENGINEERING_COMPLIANCE"."RESET_HOUR" AS "RESET_HOUR",
   "ENGINEERING_COMPLIANCE"."RESET_MINUTE" AS "RESET_MINUTE",
   MAX ( "ENGINEERING_COMPLIANCE"."RESET_DATE" ) AS "LAST_COMP_DATE"
FROM ENGINEERING_COMPLIANCE
GROUP BY  "ENGINEERING_COMPLIANCE"."EO"  ,
   "ENGINEERING_COMPLIANCE"."AC"  ,
   "ENGINEERING_COMPLIANCE"."PN"  ,
   "ENGINEERING_COMPLIANCE"."PN_SN" , 
   "ENGINEERING_COMPLIANCE"."HOURS_RESET" ,
   "ENGINEERING_COMPLIANCE"."MINUTES_RESET" ,
   "ENGINEERING_COMPLIANCE"."CYCLES_RESET" ,
   "ENGINEERING_COMPLIANCE"."RESET_DATE",
   "ENGINEERING_COMPLIANCE"."RESET_HOUR" ,
   "ENGINEERING_COMPLIANCE"."RESET_MINUTE"

【讨论】：