在 SQL Server 中使用 XQuery 比较两组 XML 数据

Question

假设我将员工数据存储在日志表的xml 列中。有时还会从存储过程中更新xml 列中的数据。

这里是示例

DECLARE @XML1 XML
DECLARE @XML2 XML

SET @XML1 = 
'<NewDataSet> 
<Employee>
<EmpID>1005</EmpID>
<Name> keith </Name>
<DOB>12/02/1981</DOB>
<DeptID>ACC001</DeptID>
<Salary>10,500</Salary>
</Employee>
</NewDataSet>'

SET @XML2 = 
'<NewDataSet> 
<Employee>
<EmpID>1006</EmpID>
<Name> keith </Name>
<DOB>05/02/1981</DOB>
<DeptID>ACC002</DeptID>
<Salary>10,900</Salary>
</Employee>
</NewDataSet>'

xml 的两个数据存在一些差异，我需要将它们显示为旧值和新值作为 sql 的输出

Old Value             New Value
---------             ---------
1005                  1006
12/02/1981            05/02/1981
ACC001                ACC002
10,500                10,900

我只需要像上面那样显示差异。所以请指导我如何使用 XQuery 比较两个 xml 数据，并在 SQL Server 中仅以上述方式显示差异。请用代码 sn-p 指导我。谢谢

Answer 1

;with XML1 as
(
  select T.N.value('local-name(.)', 'nvarchar(100)') as NodeName,
         T.N.value('.', 'nvarchar(100)') as Value
  from @XML1.nodes('/NewDataSet/Employee/*') as T(N)
),
XML2 as
(
  select T.N.value('local-name(.)', 'nvarchar(100)') as NodeName,
         T.N.value('.', 'nvarchar(100)') as Value
  from @XML2.nodes('/NewDataSet/Employee/*') as T(N)
)
select coalesce(XML1.NodeName, XML2.NodeName) as NodeName, 
       XML1.Value as Value1, 
       XML2.Value as Value2
from XML1
  full outer join XML2
    on XML1.NodeName = XML2.NodeName
where coalesce(XML1.Value, '') <> coalesce(XML2.Value, '')    

结果：

NodeName             Value1               Value2
-------------------- -------------------- --------------------
EmpID                1005                 1006
DOB                  12/02/1981           05/02/1981
DeptID               ACC001               ACC002
Salary               10,500               10,900

Answer 2

我没有你想要的 exact 输出 - 但至少你可以很好地比较新旧值：

;WITH OldData AS
(
SELECT 
    @XML1.value('(/NewDataSet/Employee/EmpID)[1]', 'int') AS 'EmpID',
    @XML1.value('(/NewDataSet/Employee/Name)[1]', 'varchar(50)') AS 'Name',
    @XML1.value('(/NewDataSet/Employee/DOB)[1]', 'datetime') AS 'DOB',
    @XML1.value('(/NewDataSet/Employee/DeptID)[1]', 'varchar(50)') AS 'DeptID',
    @XML1.value('(/NewDataSet/Employee/Salary)[1]', 'varchar(25)') AS 'Salary'
),
NewData AS
(
SELECT 
    @XML2.value('(/NewDataSet/Employee/EmpID)[1]', 'int') AS 'EmpID',
    @XML2.value('(/NewDataSet/Employee/Name)[1]', 'varchar(50)') AS 'Name',
    @XML2.value('(/NewDataSet/Employee/DOB)[1]', 'datetime') AS 'DOB',
    @XML2.value('(/NewDataSet/Employee/DeptID)[1]', 'varchar(50)') AS 'DeptID',
    @XML2.value('(/NewDataSet/Employee/Salary)[1]', 'varchar(25)') AS 'Salary'
)
SELECT
    'Old values', od.*
FROM OldData od
UNION
SELECT 'New values', nd.*
FROM NewData nd

给你一个输出：

            EmpID  Name   DOB                       DeptID   Salary
Old values  1005   keith  1981-12-02 00:00:00.000   ACC001   10,500
New values  1006   keith  1981-05-02 00:00:00.000   ACC002   10,900

SQL Server 非常适合存储和操作数据 - 但这样的演示应该在前端应用程序（如 ASP.NET 应用程序）中完成 - 而不是在 T-SQL... .

Answer 3

我来晚了！！！但是我发现如果上面显示的员工 XML 有多个记录，那么使用 CTE 的 JOIN 查询会返回不正确的结果。

我有以下 XML 输入

DECLARE @XML1 XML
DECLARE @XML2 XML

SET @XML1 = 
'<NewDataSet> 
<Employees>
    <Employee>
        <Name> keith </Name>
        <EmpID> 1005 </EmpID>
        <DOB>12/02/1981</DOB>
        <DeptID>ACC001</DeptID>
        <Salary>10,500</Salary>
    </Employee>
    <Employee>
        <Name> keith </Name>
        <EmpID> 1004 </EmpID>
        <DOB>12/02/1981</DOB>
        <DeptID>ACC001</DeptID>
        <Salary>10,500</Salary>
    </Employee>
</Employees>
</NewDataSet>'

    SET @XML2 = 
    '<NewDataSet> 
    <Employees>
        <Employee>
            <Name> keith </Name>
            <EmpID> 1005 </EmpID>
            <DOB>12/02/1981</DOB>
            <DeptID>ACC001</DeptID>
            <Salary>10,500</Salary>
        </Employee>
        <Employee>
            <Name> keith </Name>
            <EmpID> 1004 </EmpID>
            <DOB>12/02/1981</DOB>
            <DeptID>ACC001</DeptID>
            <Salary>10,501</Salary>
        </Employee>
        <Employee>
            <Name> keith1 </Name>
            <EmpID> 10040 </EmpID>
            <DOB>12/02/1981</DOB>
            <DeptID>ACC001</DeptID>
            <Salary>10,501</Salary>
        </Employee>
    </Employees>
    </NewDataSet>'

我将使用下面的查询来找出差异

select  T.N.value('local-name(.)', 'nvarchar(100)') as NodeName,
T.N.value('.', 'nvarchar(100)') as Value
from @XML2.nodes('/NewDataSet/Employees/Employee/*') as T(N)

EXCEPT

select  T.N.value('local-name(.)', 'nvarchar(100)') as NodeName,
T.N.value('.', 'nvarchar(100)') as Value
from @XML1.nodes('/NewDataSet/Employees/Employee/*') as T(N)

希望对你有帮助！！！