sql-server - SQL Server XML添加多个不同类型的节点

Question

我希望以此格式创建输出 xml，但无法在“子项”下添加“功能”和“类别”节点。我可以一次添加一个，但不能同时添加两个。

<Parent>
    <Child>
        <Features>
            <Feature Id="f1" />
            <Feature Id="f2" />
            <Feature Id="f3" />
        </Features>
        <Categories>
            <Category Name="c1">
                <Feature>f1</Feature>
                <Feature>f2</Feature>
            </Category>
            <Category Name="c2">
                <Feature>f2</Feature>
                <Feature>f3</Feature>
            </Category>
            <Category Name="c3">
                <Feature>f2</Feature>
            </Category>
    </Child>
</Parent>

这是我的 SQL，用于创建两个带有 <Features> 的 XML 字符串。节点和 <Category>节点:

DECLARE @CategoryFeatures TABLE (CategoryId VARCHAR(5), FeatureId VARCHAR(5))

INSERT INTO @CategoryFeatures VALUES ('c1', 'f1')
INSERT INTO @CategoryFeatures VALUES ('c1', 'f2')
INSERT INTO @CategoryFeatures VALUES ('c2', 'f2')
INSERT INTO @CategoryFeatures VALUES ('c2', 'f3')
INSERT INTO @CategoryFeatures VALUES ('c3', 'f2')

SELECT 
(
    SELECT
    (
        SELECT [@Id] = FeatureId
        FROM CategoryFeatures
        GROUP BY FeatureId
        FOR XML PATH ('Feature'), ROOT ('Features'), TYPE)
    FOR XML PATH ('Child'), TYPE)
FOR XML PATH ('Parent')


SELECT 
(
    SELECT
    (
        SELECT [@Name] = cat.CategoryId,
        (
            SELECT Feature = cf.FeatureId
            FROM CategoryFeatures cf
            WHERE cf.CategoryId = cat.CategoryId
            FOR XML PATH (''), TYPE)
        FROM CategoryFeatures cat
        GROUP BY cat.CategoryId
        FOR XML PATH ('Category'), ROOT ('Categories'), TYPE)
    FOR XML PATH ('Child'), TYPE)
FOR XML PATH ('Parent')

如何使这两个节点处于同一级别，使其看起来像上面的预期输出？谢谢。

Answer 1

一种可能性是子查询的狂欢。

SELECT (SELECT (SELECT cf1.featureid "Feature/@Id"
                       FROM (SELECT DISTINCT
                                    cf0.featureid
                                    FROM @categoryfeatures cf0) cf1
                       FOR XML PATH(''),
                               TYPE)
               FOR XML PATH('Features'),
                       TYPE),
       (SELECT (SELECT cf1.categoryid "Category/@Name",
                       (SELECT cf2.featureid "Feature"
                               FROM @categoryfeatures cf2
                               WHERE cf2.categoryid = cf1.categoryid
                               FOR XML PATH(''),
                                       TYPE) "Category"
                       FROM (SELECT DISTINCT
                                    cf0.categoryid
                                    FROM @categoryfeatures cf0) cf1
                       FOR XML PATH(''),
                               TYPE)
               FOR XML PATH('Categories'),
                       TYPE)
       FOR XML PATH('Child'),
               ROOT('Parent');

db<>fiddle