sql - 使用交叉应用将列转置为行

Question

源数据

+--------+-------+---------------+------------+--------+--------------+-------+
| RowNum | SeqNo |     Name      | NameReason | Gender | GenderReason |  ID   |
+--------+-------+---------------+------------+--------+--------------+-------+
|      1 | A123  | IronMan       |            | P      |              | E8888 |
|      2 | A123  | CaptainMarvel | A          | L      | A            | E8888 |
|      3 | A123  | Yoooo         |            |        |              | E8888 |
|      4 | A123  | Heyyy         |            |        |              | E8888 |
|      1 | B456  | Hey           |            |        |              | D2222 |
|      2 | B456  | DOTS          | A          |        |              | D2222 |
|      1 | C1234 | Hulk          |            |        |              | E8989 |
|      2 | C1234 | Cap           |            |        |              | E8989 |
|      3 | C1234 | Hat           |            |        |              | E8989 |
+--------+-------+---------------+------------+--------+--------------+-------+

我想要的结果

+-------+-------+---------+---------------+----------+--------+
| SeqNo |  ID   | ColName |  From_Value   | To_Value | Reason |
+-------+-------+---------+---------------+----------+--------+
| A123  | E8888 | Name    | CaptainMarvel | IronMan  | A      |
| A123  | E8888 | Gender  | L             | P        | A      |
| B456  | D2222 | Name    | DOTS          | Hey      | A      |
| C1234 | E8989 | Name    | Cap           | Hulk     |        |
+-------+-------+---------+---------------+----------+--------+

查询:

select a.rownum, a.seqno, a.name, a.id,
       b.*
from #A a cross apply
( values ('Name', NameReason)
         ('Gender', GenderReason)
    ) b (colname, Reason)
where reason is not null

注:要查找变化。 RowNum=1 是最新更新 (To_Value)，RowNum=2 (From_Value)。 rownum 已经过滤了顶部更新的结果 (rownumber() over (partitition) 。我只需要 rownum=2(from_Value), rownum=1(to_value) 其他忽略，因为1 个应用程序可以更新 100 次，我只需要找到最新的更改即可。

从上面的查询中，如何修改为我想要的结果？我如何添加 from_value 和 to_value，原因？

Answer 1

假设您可以在 RowNum + 1 上链接“From”记录

SELECT q.SeqNo, q.ToName AS Name, q.ID, ca.ColName, ca.From_Value, ca.To_Value 
FROM
(
  SELECT 
   a1.ID, a1.SeqNo, a1.NameReason, a1.GenderReason, a1.RowNum, 
   a2.Name as FromName, a1.Name as ToName,
   a2.Gender AS FromGender, a1.Gender AS ToGender
  FROM #A a1
  JOIN #A a2 ON (a2.ID = a1.ID AND a2.RowNum = a1.RowNum + 1)
  WHERE (a1.NameReason IS NOT NULL OR a1.GenderReason IS NOT NULL)
    AND a1.Name != a2.Name
) q
CROSS APPLY (VALUES 
 (1, 'Name', NameReason, FromName, ToName), 
 (2, 'Gender', GenderReason, FromGender, ToGender)
) ca (ColSeq, ColName, Reason, From_Value, To_Value)
WHERE ca.Reason IS NOT NULL
ORDER BY q.SeqNo, ca.ColSeq;

但根据评论，只有 RowNum 1 和 2 很重要。
然后就可以简化了。

SELECT q.SeqNo, q.ToName AS Name, q.ID, ca.ColName, ca.From_Value, ca.To_Value 
FROM
(
  SELECT 
   a1.ID, a1.SeqNo, 
   a1.NameReason, a2.Name as FromName, a1.Name as ToName,
   a1.GenderReason, a2.Gender AS FromGender, a1.Gender AS ToGender
  FROM #A a1
  JOIN #A a2 ON (a2.ID = a1.ID AND a2.RowNum = 2)
  WHERE a1.RowNum = 1
) q
CROSS APPLY (VALUES 
 (1, 'Name', NameReason, FromName, ToName), 
 (2, 'Gender', GenderReason, FromGender, ToGender)
) ca (ColSeq, ColName, Reason, From_Value, To_Value)
WHERE ca.Reason IS NOT NULL
ORDER BY q.SeqNo, ca.ColSeq;

结果:

SeqNo Name    ID    ColName From_Value    To_Value
----- ------- ----- ------- ------------- --------
A123  IronMan E8888 Name    CaptainMarvel IronMan
A123  IronMan E8888 Gender  L             P
B456  Hey     D2222 Name    DOTS          Hey

db<>fiddle here 测试