Tsql 从 table 创建 Xml

Question

我在 SQL 服务器中有一个 table，我想以 xml 格式获取数据。

我的table长得像

Year | Semester | Room | Professor
-----+----------+------+-----------    
2013 |    1     | 101  | Li
2013 |    1     | 102  | wang
2013 |    1     | 103  | Rob
2013 |    2     | 204  | jess
2013 |    2     | 205  | Mat
2014 |    1     | 104  | Li
2014 |    1     | 105  | wang
2014 |    1     | 106  | Rob
2014 |    2     | 206  | jess
2014 |    2     | 207  | Mat

我想要这样的 Xml 格式：

<St>
  <Year id="2013">
    <Semester nb="1">
      <data>
        <Room>101</Room>
        <professor>Li</kwh>
      </data>
      <data>
        <Room>102</Room>
        <professor>wang</kwh>
      </data>
    </Semester>
    <Semester nb="2">
      <data>
        <Room>204</Room>
        <professor>jess</kwh>
      </data>
     </Semester>
  <Year>
 <Year id="2014">
    <Semester nb="1">
     ...
    </Semester>
    <Semester nb="2">
    ...
     </Semester>
  <Year>
</St>

现在我的代码是：

SELECT 
    Year as "@id", 
    Semester as "Semester /@nb", 
    Room as "Semester/data/Room", 
    Professor as "Semester/data/Professor " 
FROM 
    checking
FOR XML Path ('Year'), root ('St')

哪个给我这个xml:

<St>   
<Year id="2013">
<Semester nb="1">
 <data>
        <Room>101</Room>
        <Professor>Li</Professor>
     </data>
   </Semester>   </Year>   <Year id="2013">
    <Semester nb="1">
      <data>
        <Room>102</Room>
        <Professor>wang</Professor>
    </data>
    </Semester>   </Year>   <Year id="2013">
   <Semester nb="1">
     <data>
       <Room>103</Room>
      <Professor>rob</Professor>
     </data>
    </Semester>   
</Year>
 ... 
</St>

我非常接近解决方案，但找不到如何按年和学期对其进行分组。

我尝试了 group by 和 order by，但 none 有效。

Answer 1

使用分组依据和相关子查询。

declare @T table
(
  Year int,
  Semester int,
  Room int,
  Professor varchar(10)
);

insert into @T values
(2013, 1, 101, 'Li  '),
(2013, 1, 102, 'wang'),
(2013, 1, 103, 'Rob '),
(2013, 2, 204, 'jess'),
(2013, 2, 205, 'Mat '),
(2014, 1, 104, 'Li  '),
(2014, 1, 105, 'wang'),
(2014, 1, 106, 'Rob '),
(2014, 2, 206, 'jess'),
(2014, 2, 207, 'Mat ');

select T1.Year as [@id],
       (
       select T2.Semester as [@nb],
              (
              select T3.Room,
                     T3.Professor
              from @T as T3
              where T3.Year = T2.Year and
                    T3.Semester = T2.Semester
              for xml path('data'), type
              )
       from @T as T2
       where T1.Year = T2.Year
       group by T2.Semester, T2.Year
       for xml path('Semester'), type
       )
from @T as T1
group by T1.Year
for xml path('Year'), root('St');

结果：

<St>
  <Year id="2013">
    <Semester nb="1">
      <data>
        <Room>101</Room>
        <Professor>Li  </Professor>
      </data>
      <data>
        <Room>102</Room>
        <Professor>wang</Professor>
      </data>
      <data>
        <Room>103</Room>
        <Professor>Rob </Professor>
      </data>
    </Semester>
    <Semester nb="2">
      <data>
        <Room>204</Room>
        <Professor>jess</Professor>
      </data>
      <data>
        <Room>205</Room>
        <Professor>Mat </Professor>
      </data>
    </Semester>
  </Year>
  <Year id="2014">
    <Semester nb="1">
      <data>
        <Room>104</Room>
        <Professor>Li  </Professor>
      </data>
      <data>
        <Room>105</Room>
        <Professor>wang</Professor>
      </data>
      <data>
        <Room>106</Room>
        <Professor>Rob </Professor>
      </data>
    </Semester>
    <Semester nb="2">
      <data>
        <Room>206</Room>
        <Professor>jess</Professor>
      </data>
      <data>
        <Room>207</Room>
        <Professor>Mat </Professor>
      </data>
    </Semester>
  </Year>
</St>

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