如何在XML中处理空值

Question

我正在比较表中两行之间的数据，因为我想知道在哪些列中存在差异。因此，我编写了具有SQL Server XML功能的代码。

例如，我创建了一个包含FirstName，LastName和BirthDate的表。数据来自不同的来源。我想确保两个来源都为我提供相同的数据。如果不是这种情况，我将在结果中指出关注的列及其值

Id    Source    FirstName    LastName    Birthday
1     1         Toto         Titi        2001-01-30
1     2         Totos        Titi        NULL

如您所见，我的生日列为空值。 *我的问题：如何将null值与xml中的数据进行比较。谢谢您的帮助

我的SQL代码：

CREATE TABLE dbo.MyTable
(
    Id int,
    Source int,
    FirstName varchar(100),
    LastName varchar(100),
    Birthday Date
)
INSERT INTO dbo.MyTable
VALUES(1, 1, 'Toto', 'Titi', '2001/01/30'), (1, 2, 'Totos', 'Titi', NULL)

-------------------------
with A
as (
 select Id, Source,  (
         Select  *
         from    dbo.MyTable
         where   Id = pp.Id and Source = pp.Source
         for xml auto, type) as X
 from dbo.MyTable pp
 )
--select * from A

, B
as (
    select  Id, Source
        ,   X.query(
         'for $f in dbo.MyTable/@*
          return 
        <MyTable name="{ local-name($f) }" value="{ data($f) }" />
      ') as X2
 from A
 )
--select * from B

, C
as (
 select B.Id as ID, B.Source
  , norm.MyTable.value('@name', 'varchar(max)') as Name
  , norm.MyTable.value('@value', 'varchar(max)') as Value
from B
 cross apply B.X2.nodes('/MyTable') as norm(MyTable)
)
--select * from C

-- Result
select C1.Source, C1.Id, C1.Name as ColumnName, C1.Value as ColumnValue
from (select * from C) C1
full outer join (select * from C) C2
    on C1.Name = c2.Name and C1.ID = C2.ID
where c1.Value <> c2.Value and C1.Name <> 'Source'
order by C1.ID, C1.Name

此代码的结果：

Source    Id    ColumnName    ColumnValue
1         1     FirstName     Toto
2         1     FirstName     Totos

结果是，我想在ColumnName及其值中看到Birthday 这是我的预期结果：

Source  Id  ColumnName  ColumnValue
1   1   Birthday    2001-01-30
1   1   FirstName   Toto
1   2   Birthday    NULL
2   1   FirstName   Totos