如何在Oracle中按日期分組和排序？

Question

我運行這個 SQL 請求：

SELECT Max(scaleA.val) AS scaleA_val,
       Max(scaleB.val) AS scaleB_val,
       To_char(From_dt1970(scaleA.time1970), 'DD') AS day
  FROM rsdu2elarh.el008_6305119 scaleA
  FULL OUTER JOIN rsdu2elarh.el008_6305126 scaleB
    ON scaleA.time1970 = scaleB.time1970
 WHERE scaleA.time1970 > To_dt1970(To_date('2019/11/01', 'yyyy/mm/dd'))
   AND scaleA.time1970 < To_dt1970(To_date('2019/12/01', 'yyyy/mm/dd'))
 GROUP BY 'day'
 ORDER BY 'day'

並返回：

但它不是按日期排序的。 如何讓請求顯示按日期排序的數據？ 我所有的嘗試都導致“不是按表達式分組”或許多重復的字段:(

Answer 1

如果使用 GROUP BY 子句，則 SELECT 或 ORDER BY 中的任何表達式，它不是組函數（或聚合函數或聚合列），如 COUNT、AVG、MIN、MAX、SUM 等（聚合函數列表）應為存在於 GROUP BY 子句中。

例1：（這里employee_id不是分組函數，所以必須出現在GROUP BY中。相比之下，sum(salary)是分組函數（聚合列），所以不需要出現在GROUP BY子句中。

SELECT employee_id, sum(salary) 
FROM employees
GROUP BY employee_id
ORDER BY employee_id; 

示例 2：這將導致“not a group by expression”錯誤。

SELECT employee_id, sum(salary) 
FROM employees;  

要更正，您需要執行以下操作之一：

將 SELECT 和 ORDER BY 子句中列出的所有非聚合表達式包含在 GROUP BY 子句中。

Answer 2

您不能使用未分組的列進行排序，因為相同的日期可能出現在多個組中，因此如果您想按DD排序，則可以在order by子句中使用它，如下所示：

SELECT  MAX(scaleA.VAL) AS scaleA_val, MAX(scaleB.VAL) AS scaleB_val FROM RSDU2ELARH.EL008_6305119 scaleA 
FULL OUTER JOIN RSDU2ELARH.EL008_6305126 scaleB ON scaleA.time1970 = scaleB.time1970 
WHERE scaleA.time1970 > TO_DT1970(TO_DATE ('2019/11/01', 'yyyy/mm/dd')) AND scaleA.time1970 < TO_DT1970(TO_DATE ('2019/12/01', 'yyyy/mm/dd')) 
GROUP BY TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD')
-- use this order by clause
Order by TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD')

干杯！！

Answer 3

您可以嘗試將TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD')也添加到 SELECT 列表中，將其別名並在 ORDER BY Clause 中使用：

SELECT TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD') AS myDay,
       MAX(scaleA.VAL) AS scaleA_val, 
       MAX(scaleB.VAL) AS scaleB_val
  FROM RSDU2ELARH.EL008_6305119 scaleA
  FULL OUTER JOIN RSDU2ELARH.EL008_6305126 scaleB
    ON scaleA.time1970 = scaleB.time1970
 WHERE scaleA.time1970 > TO_DT1970(DATE'2019-11-01')
   AND scaleA.time1970 < TO_DT1970(DATE'2019-12-01')
 GROUP BY TO_CHAR(FROM_DT1970(scaleA.time1970), 'DD')
 ORDER BY myDay

而列別名不能用於 GROUP BY 子句。

Answer 4

您的查詢中唯一缺少的是我們不能在 group by 子句中使用別名，但是可以在 order by 子句中使用別名，因此下面的查詢將起作用。

SELECT Max(scaleA.val) AS scaleA_val,
       Max(scaleB.val) AS scaleB_val,
       To_char(From_dt1970(scaleA.time1970), 'DD') AS day
  FROM rsdu2elarh.el008_6305119 scaleA
  FULL OUTER JOIN rsdu2elarh.el008_6305126 scaleB
    ON scaleA.time1970 = scaleB.time1970
 WHERE scaleA.time1970 > To_dt1970(To_date('2019/11/01', 'yyyy/mm/dd'))
   AND scaleA.time1970 < To_dt1970(To_date('2019/12/01', 'yyyy/mm/dd'))
 GROUP BY To_char(From_dt1970(scaleA.time1970), 'DD')
 ORDER BY day;

如果要使用別名，則需要使用子查詢

SELECT Max(scaleA_val)  AS scaleA_val,
       Max(scaleB_val) AS scaleB_val,
       day from
       (select scaleA.val  scaleA_val,
        scaleB.val AS scaleB_val,
        To_char(From_dt1970(scaleA.time1970), 'DD') AS day
  FROM rsdu2elarh.el008_6305119 scaleA
  FULL OUTER JOIN rsdu2elarh.el008_6305126 scaleB
    ON scaleA.time1970 = scaleB.time1970
 WHERE scaleA.time1970 > To_dt1970(To_date('2019/11/01', 'yyyy/mm/dd'))
   AND scaleA.time1970 < To_dt1970(To_date('2019/12/01', 'yyyy/mm/dd'))
   )
 GROUP BY day
 ORDER BY day;