跟踪T-SQL中每个表列的数据更改

Question

给定下表，我想获取两列price和每个fruit值的qty变化的历史记录。 我正在使用MS SQL Server 2012。

因此，例如：

• 第1行和第3行之间的变化是苹果的价格从10升至30，这在下面的结果表中给出了第1行。
• 第2行和第4行之间的变化是，香蕉的价格从20变为30，数量从2变为3，这在结果表中给出了第2和3行。

有没有办法做到这一点？ 有没有办法有效地做到这一点？

源表

+----+---------+--------+--------+---------+
| id | fruit   | price  | qty    | created |
+----+---------+--------+--------+---------+
| 1  | apples  | 10     | 1      | 1/1/16  |
+----+---------+--------+--------+---------+
| 2  | bananas | 20     | 2      | 1/1/16  |
+----+---------+--------+--------+---------+
| 3  | apples  | 30     | 1      | 2/1/16  |
+----+---------+--------+--------+---------+
| 4  | bananas | 30     | 3      | 2/1/16  |
+----+---------+--------+--------+---------+
| 5  | apples  | 30     | 2      | 3/1/16  |
+----+---------+--------+--------+---------+
| 6  | apples  | 30     | 3      | 7/1/16  |
+----+---------+--------+--------+---------+

结果表

+----+----+--------+--------+--------+---------+
| id | fk | col    | oldval | newval | changed |
+----+----+--------+--------+--------+---------+
| 1  | 3  | price  | 10     | 30     | 2/1/16  |
+----+----+--------+--------+--------+---------+
| 2  | 4  | price  | 20     | 30     | 2/1/16  |
+----+----+--------+--------+--------+---------+
| 3  | 4  | qty    | 2      | 3      | 2/1/16  |
+----+----+--------+--------+--------+---------+
| 4  | 5  | qty    | 1      | 2      | 3/1/16  |
+----+----+--------+--------+--------+---------+
| 5  | 6  | qty    | 2      | 3      | 7/1/16  |
+----+----+--------+--------+--------+---------+

Answer 1

这是一种方法：

;WITH LagCTE AS (
  SELECT  id, fruit, price, qty, created,
          LAG(price) OVER (PARTITION BY fruit 
                           ORDER BY created) AS prevPrice,
          LAG(qty) OVER (PARTITION BY fruit 
                         ORDER BY created) AS prevQty
  FROM mytable
)
SELECT ROW_NUMBER() OVER (ORDER BY changed) AS id,
       fk, col, oldval, newval, changed
FROM (       
  SELECT id AS fk, fruit, 'price' AS col, 
         prevPrice AS oldval, price AS newval, 
         created AS changed
  FROM LagCTE
  WHERE prevPrice <> price

  UNION ALL 

  SELECT id AS fk, fruit, 'qty' AS col, 
         prevQty AS oldval, qty AS newval, 
         created AS changed
  FROM LagCTE
  WHERE prevQty <> qty) AS t

在这里演示

Answer 2

以下答案的前提条件是price和qty具有相同的数据类型，并且id是IDENTITY列。

第一步是找到更改。 您可以通过对id排序的同一水果的所有记录进行id ，然后加入后续记录来做到这一点。 然后，你可以UNPIVOT结果，并进行过滤不变colums。

WITH
   SourceNumbered AS
      (
         SELECT
               ROW_NUMBER() OVER(PARTITION BY fruit ORDER BY id) AS nr,
               id, fruit, price, qty, created
            FROM
               SourceTable
      ),
   SourceUnpivoted AS
      (
         SELECT
               U.id, U.fk, U.col
            FROM
               (
                  SELECT
                        L.id, R.id AS fk,
                        L.price - R.price AS price,
                        L.qty - R.qty AS qty
                     FROM
                        SourceNumbered L
                        INNER JOIN SourceNumbered R
                           ON R.fruit = L.fruit
                              AND R.nr = L.nr + 1
               ) D
            UNPIVOT (value FOR col IN (price, qty)) U
            WHERE
               value != 0
      )
SELECT
      U.id, U.fk, U.col,
      CASE U.col
         WHEN 'price'
            THEN O.price
         WHEN 'qty'
            THEN O.qty
      END AS oldval,
      CASE U.col
         WHEN 'price'
            THEN N.price
         WHEN 'qty'
            THEN N.qty
      END AS oldval,
      N.created AS changed
   FROM
      SourceUnpivoted U
      INNER JOIN SourceTable O
         ON O.id = U.id
      INNER JOIN SourceTable N
         ON N.id = U.fk;

由于您不能取消旋转多于一列，因此最终SELECT情况不可避免。