將行轉換為列-面臨問題。

Question

我有以下數據集（請注意，我的數據庫/方案有些復雜，因此在此處包括所有詳細信息是不可行的）

這是我從基本表中提取並創建view數據的簡化版本。

workout_activity_record_id  attribute_metric_id attribute_metric_value  workout_exercise_set_created_on
234                                17              10                          2012-02-06 00:00:00
234                                18              30                          2012-02-06 00:00:00
234                                17              20                          2012-03-03 00:00:00
234                                18              12.9                        2012-03-03 00:00:00
234                                17              20                          2012-04-02 00:00:00
234                                18              40                          2012-04-02 00:00:00
.
.
. (So on for further workout_activity_record_ids)

我需要計算（在數據中查找以更好地理解）

Grand Total = (10 * 30) + (20 * 12.9) + (20 * 40)

按月分組。

一種有助於乘法的基本方法是將行轉置為列。 因此上述結構將變為-

SELECT
       CASE attribute_metric_id
           WHEN '17' THEN attribute_metric_value END AS 'ex17',
       CASE attribute_metric_id WHEN '18' THEN attribute_metric_value END AS 'ex18', 
       workout_exercise_set_created_on
FROM exercise_attribute
WHERE workout_activity_record_id =234

為此，我經歷了幾篇SO文章，並嘗試了各種可行/不可行（：D）選項之后，提出了以下查詢。

workout_activity_record_id  ex17    ex18    workout_exercise_set_created_on 
234                          10      NULL   2012-02-06 00:00:00
234                          NULL    30     2012-02-06 00:00:00
234                          20      NULL   2012-03-03 00:00:00
234                          NULL    12.9   2012-03-03 00:00:00
234                          20      NULL   2012-04-06 00:00:00
234                          NULL    40     2012-04-02 00:00:00

我得到的實際輸出是

\n execution_activity_record_id ex17 ex18 Exercise_exercise_set_created_on \n 234 10空2012-02-06 00:00:00\n 234空30 2012-02-06 00:00:00\n 234 20空2012-03-03 00:00:00\n 234空12.9 2012-03-03 00:00:00\n 234 20空2012-04-06 00:00:00\n 234空40 2012-04-02 00:00:00\n

任何人都可以對此有所了解嗎？ 我將不勝感激。 謝謝！

Answer 1

這將為您計算總計，按年份和月份分組：

SELECT YEAR(workout_exercise_set_created_on) AS YEAR,
       MONTH(workout_exercise_set_created_on) AS MONTH,
       sum(SubTotal) AS GrandTotal
FROM
  (SELECT workout_exercise_set_created_on,
          max(CASE WHEN attribute_metric_id = 17 THEN attribute_metric_value END) * max(CASE WHEN attribute_metric_id = 18 THEN attribute_metric_value END) AS SubTotal
   FROM MyTable
   GROUP BY workout_exercise_set_created_on) a
GROUP BY YEAR(workout_exercise_set_created_on),
         MONTH(workout_exercise_set_created_on)

SQL小提琴示例

產量

YEAR    MONTH   GRANDTOTAL
2012    2        300
2012    3        258
2012    4        800

Answer 2

只需添加聚合函數：

SELECT
   MAX(CASE attribute_metric_id
        WHEN '17' THEN attribute_metric_value 
      END) AS 'ex17',
   MAX(CASE attribute_metric_id 
        WHEN '18' THEN attribute_metric_value 
       END) AS 'ex18', 
   workout_exercise_set_created_on
   FROM exercise_attribute
   WHERE workout_activity_record_id =234
   GROUP BY workout_exercise_set_created_on

如果您需要顯示不同的workout_activity_record_id結果， workout_activity_record_id應按group by workout_activity_record_id,workout_exercise_set_created_on修改group by workout_activity_record_id,workout_exercise_set_created_on