如何根据 SQL 中的现有值更新 XML 属性？

Question

我在应用程序中有很多 XML 文档存储在 SQL 服务器数据库中。这是一个例子：

<para id="19" revDate="2022-05-04T04:00:00Z">
  <emphasis>
    <emphasis color="Blue">test</emphasis>
    <emphasis color="Red">test</emphasis>
  </emphasis>
  <emphasis>
    <emphasis color="Green">test</emphasis>
  </emphasis>
</para>

我想替换所有 emphasis 和 entry 元素的 color 属性值与相应的十六进制颜色代码。这就是我想要得到的：

<para id="19" revDate="2022-05-04T04:00:00Z">
  <emphasis>
    <emphasis color="0000FF">test</emphasis>
    <emphasis color="FF0000">test</emphasis>
  </emphasis>
  <emphasis>
    <emphasis color="008000">test</emphasis>
  </emphasis>
</para>

所以我需要某种 switch/case。注意：属性可以有任何十六进制值（不仅仅是红色、绿色、蓝色）：

DECLARE @ColorTextValue VARCHAR(20) = 'Blue'
DECLARE @ColorHexValue VARCHAR(6)
SET @ColorHexValue = CASE @ColorTextValue
    WHEN 'Blue' THEN '0000FF'           
    WHEN 'Red' THEN 'FF0000'
    WHEN 'Green' THEN '008000'
END

我现在有以下脚本：

DECLARE @tbl TABLE (XmlData XML);
INSERT INTO @tbl VALUES
('<para id="19" revDate="2022-05-04T04:00:00Z">
    <emphasis>
      <emphasis color="Blue">test</emphasis>
      <emphasis color="Red">test</emphasis>
    </emphasis>
    <emphasis>
      <emphasis color="Green">test</emphasis>
    </emphasis>
  </para>'
);

UPDATE 
  [XmlDocument]
SET
  [XmlData].modify('replace value of (//*[self::emphasis or self::entry]/@color)[1] with "hexCodeHere"')
FROM 
  @tbl AS [XmlDocument]
WHERE 
  [XmlDocument].[XmlData].exist('//*[self::emphasis or self::entry][@color]') = 1


SELECT * FROM @tbl

如您所见，它只有一个硬编码的 HexCode。如何在此语句中添加某种开关以动态计算十六进制代码？此外，它不可能更新所有属性。它只更新第一项

Answer 1

请尝试以下解决方案。

它在 CTE 中创建一个计算列 ColorHexValue。

下一步是用 ColorHexValue 列值更新 XML 列 color 属性。

SQL

-- DDL and sample data population, start
DECLARE @tbl TABLE (ID INT IDENTITY PRIMARY KEY, xmldata XML);
INSERT INTO @tbl (xmldata) VALUES
(N'<para id="19" revDate="2022-05-04T04:00:00Z">
  <emphasis>
    <emphasis color="Blue">test</emphasis>
  </emphasis>
</para>'),
(N'<para id="19" revDate="2022-05-04T04:00:00Z">
  <emphasis>
    <emphasis color="Green">test</emphasis>
  </emphasis>
</para>');
-- DDL and sample data population, end

-- just to see
SELECT * 
FROM @tbl
CROSS APPLY (SELECT CASE xmldata.value('(/para/emphasis/emphasis/@color)[1]', 'VARCHAR(10)')
    WHEN 'Blue' THEN '0000ff'           
    WHEN 'Red' THEN 'ff0000'
    WHEN 'Green' THEN '008000'
END) t(ColorHexValue);

-- real deal
;WITH rs AS
(
    SELECT * 
    FROM @tbl
    CROSS APPLY (SELECT CASE xmldata.value('(/para/emphasis/emphasis/@color)[1]', 'VARCHAR(10)')
        WHEN 'Blue' THEN '0000ff'           
        WHEN 'Red' THEN 'ff0000'
        WHEN 'Green' THEN '008000'
    END) t(ColorHexValue)
)
UPDATE rs 
SET xmldata.modify('replace value of (/para/emphasis/emphasis/@color)[1] with sql:column("ColorHexValue")');

-- test
SELECT * FROM @tbl;

SQL#2

-- DDL and sample data population, start
DECLARE @tbl TABLE (ID INT IDENTITY PRIMARY KEY, xmldata XML);
INSERT INTO @tbl (xmldata) VALUES
(N'<para id="19" revDate="2022-05-04T04:00:00Z">
    <emphasis>
      <emphasis color="Blue">test</emphasis>
      <emphasis color="Red">test</emphasis>
    </emphasis>
    <emphasis>
      <emphasis color="Green">test</emphasis>
    </emphasis>
  </para>'),
(N'<para id="19" revDate="2022-05-04T04:00:00Z">
  <emphasis>
    <emphasis color="Green">test</emphasis>
  </emphasis>
</para>');
-- DDL and sample data population, end

-- before
SELECT * FROM @tbl
WHERE xmldata.exist('//emphasis/@color[. = ("Blue","Red","Green")]') = 1;

DECLARE @tries INT = 0;

WHILE @@ROWCOUNT > 0 AND @tries < 100
BEGIN
UPDATE @tbl
SET xmldata.modify('replace value of (/para/emphasis/emphasis/@color[. = ("Blue","Red","Green")])[1]
    with (
        let $c := (/para/emphasis/emphasis/@color[. = ("Blue","Red","Green")])[1]
        return
        if ($c = "Blue") then "0000ff"
        else if ($c = "Red") then "ff0000"
        else if ($c = "Green") then "008000"
        else ("unknown color")
    )')
WHERE xmldata.exist('/para/emphasis/emphasis/@color[. = ("Blue","Red","Green")]') = 1;

    SET @tries += 1;
END;

-- after
SELECT * FROM @tbl;

db<>fiddle

如何根据 SQL 中的现有值更新 XML 属性？

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