Question

ID  State   Name        Department         City
1   O       George      Sales              Phoenix
1   N       George      Sales              Denver
2   O       Michael     Order Process      San diego
2   N       Michael     Marketing          San jose

我遇到了一种情况，我需要将上面的表格值转换为以下格式。（考虑顶行是列名）

ID  Column      OldValue       New Value
1   Department  Phoenix        Denver
2   Department  Order Process  Marketing
2   City        San diego      San jose

即：我需要从旧记录和新记录中捕获表的已更改列值，并将它们记录在不同的表中。但问题是我们有很多这样的表，列名和列数不同对于每张桌子。

如果有人提供了一个非常感谢的解决方案..！

提前谢谢。

Answer 1

这是你想要的吗？

 ID  Column      OldValue      New Value
 1   City        Phoenix       Denver
 2   Department  Order Process Marketing
 2   City        San Diego     San jose

这是动态代码：

DECLARE @sqlStm varchar(max);
DECLARE @sqlSelect varchar(max);

DECLARE @tablename varchar(200);
SET @tablename = 'testtable';

-- Assume table has ID column and State column.
SET @sqlSelect = ''
SET @sqlStm = 'WITH old AS
(
   SELECT *
   FROM '+@tablename+'
   WHERE State=''O''
), new AS
(
   SELECT *
   FROM '+@tablename+'
   WHERE State=''N''
)';

  DECLARE @aCol varchar(128)
  DECLARE curCols CURSOR  FOR
    SELECT column_name
    FROM information_schema.columns
    WHERE table_name = @tablename
      AND UPPER(column_name) NOT IN ('ID','STATE')

  OPEN curCols
  FETCH curCols INTO @aCol

  WHILE (@@FETCH_STATUS = 0)
  BEGIN
    SET @sqlStm = @sqlStm +
      ', changed'+@aCol+' AS
(
   SELECT n.ID, '''+@aCol+''' AS [Column], o.['+@aCol+'] AS oldValue, n.['+@aCol+'] AS newValue
   FROM new n
   JOIN old o ON n.ID = o.ID AND n.['+@aCol+'] != o.['+@aCol+']
)'
    IF LEN(@sqlSelect) > 0 SET @sqlSelect = @sqlSelect + ' UNION ALL '

    SET @sqlSelect = @sqlSelect + '
SELECT * FROM changed'+@aCol

    FETCH curCols INTO @aCol

  END

  CLOSE curCols
  DEALLOCATE curCols

    SET @sqlSelect = @sqlSelect + '
ORDER BY id, [Column]'


  PRINT @sqlStm+@sqlSelect

  EXEC (@sqlStm+@sqlSelect)

在我的测试中输出以下内容：

WITH old AS
(
   SELECT *
   FROM testtable
   WHERE State='O'
), new AS
(
   SELECT *
   FROM testtable
   WHERE State='N'
), changedName AS
(
   SELECT n.ID, 'Name' AS [Column], o.[Name] AS oldValue, n.[Name] AS newValue
   FROM new n
   JOIN old o ON n.ID = o.ID AND n.[Name] != o.[Name]
), changedDepartment AS
(
   SELECT n.ID, 'Department' AS [Column], o.[Department] AS oldValue, n.[Department] AS newValue
   FROM new n
   JOIN old o ON n.ID = o.ID AND n.[Department] != o.[Department]
), changedCity AS
(
   SELECT n.ID, 'City' AS [Column], o.[City] AS oldValue, n.[City] AS newValue
   FROM new n
   JOIN old o ON n.ID = o.ID AND n.[City] != o.[City]
)
SELECT * FROM changedName UNION ALL 
SELECT * FROM changedDepartment UNION ALL 
SELECT * FROM changedCity
ORDER BY id, [Column]

以下原始答案：

我会这样做 - 因为我认为它比其他可能更快的方式更清晰：

with old as
(
   Select ID, Name,Department,City
   From table1
   Where State='O'
), new as
(
   Select ID, Name,Department,City
   From table1
   Where State='N'
), oldDepartment as
(
   Select ID, 'Department' as Column, o.Department as oldValue, n.Department as newValue
   From new
   join old on new.ID = old.ID and new.Department != old.Department
), oldCity as
(
   Select ID, 'City' as Column, o.City as oldValue, n.City as newValue
   From new
   join old on new.ID = old.ID and new.City != old.City
)
select * from oldDepartment
union all
select * from oldCity

根据许多事情（表和索引的大小等），它实际上可能比使用枢轴或案例或分组更快。这真的取决于你的数据。如果这是一次性的运行，我会选择最简单的方法。

Answer 2

最干净的方法可能是取消数据，然后使用聚合。这确实需要为每个表自定义编码，您可以通过使用某种形式的动态SQL来概括。

对于您的特定示例，以下是该怎么做的说明：

select id, col,
       max(case when OldNew = 'Old' then value end) as OldValue,
       max(case when OldNew = 'New' then value end) as NewValue
from ((select ID, OldNew, 'Name' as col, Name as value
       from t
      ) union all
      (select ID, OldNew, 'Department' as col, Department as value
       from t
      ) union all
      (select ID, OldNew, 'City' as col, City as value
       from t
      )
     ) unpvt
group by id, col
having max(value) <> min(value) and max(value) is not null;

这是为了说明目的。与使用union all相比，可以更有效地完成unpivot，特别是在扫描很多时。这是一个更高效的版本，虽然确切的语法取决于数据库：

select id, col,
       max(case when OldNew = 'Old' then value end) as OldValue,
       max(case when OldNew = 'New' then value end) as NewValue
from (select ID, OldNew, cols.col,
             (case when cols.col = 'Name' then Name
                   when cols.col = 'Department' then Department
                   when cols.col = 'City' then City
              end) as value
      from t cross join
           (select 'Name' as col union all select 'Department' union all select 'City') cols
     ) unpvt
group by id, col
having max(value) <> min(value) and max(value) is not null;

这样效率更高，因为它通常只会扫描您的表一次，而不是像union all版本那样每列扫描一次。

在任一版本中，都隐含假设所有列都具有相同的字符类型。这在您要转换的格式中是隐含的，其中所有值都在一列中。

将更新的列值作为行转换为表

2 个答案: