在SQL Server中将单位追加到XML列值

Question

I have a table with a XML column for storing the file details. Now I want to update the size node in the XML column with KB or MB according to the value.

Sample data:

<FileInfo>
    <Field Name="Filename">PV_1_PV_4126_C-482N-25457-005_V1.pdf</Field>
    <Field Name="Created">02/21/2017</Field>
    <Field Name="Modified">02/21/2017</Field>
    <Field Name="Uploaded By">2120</Field>
    <Field Name="Uploaded On">02/21/2017</Field>
    <Field Name="Size">755</Field>
</FileInfo> 

Expected result:

<FileInfo>
    <Field Name="Filename">PV_1_PV_4126_C-482N-25457-005_V1.pdf</Field>
    <Field Name="Created">02/21/2017</Field>
    <Field Name="Modified">02/21/2017</Field>
    <Field Name="Uploaded By">2120</Field>
    <Field Name="Uploaded On">02/21/2017</Field>
    <Field Name="Size">755 KB</Field>
</FileInfo>

Sample data:

<FileInfo>
    <Field Name="Filename">PV_1_PV_4126_C-482N-25457-005_V1.pdf</Field>
    <Field Name="Created">02/21/2017</Field>
    <Field Name="Modified">02/21/2017</Field>
    <Field Name="Uploaded By">2120</Field>
    <Field Name="Uploaded On">02/21/2017</Field>
    <Field Name="Size">1024</Field>
</FileInfo>

Expected result:

<FileInfo>
    <Field Name="Filename">PV_1_PV_4126_C-482N-25457-005_V1.pdf</Field>
    <Field Name="Created">02/21/2017</Field>
    <Field Name="Modified">02/21/2017</Field>
    <Field Name="Uploaded By">2120</Field>
    <Field Name="Uploaded On">02/21/2017</Field>
    <Field Name="Size">1 MB</Field>
</FileInfo>

Answer 1

You can use an updateable CTE

DECLARE @dummy TABLE(YourXMLColumn XML);
INSERT INTO @dummy VALUES
(
    N'<FileInfo>
        <!--More fields-->
        <Field Name="Size">755</Field>
    </FileInfo> '
)
,(
    N'<FileInfo>
        <!--More fields-->
        <Field Name="Size">1024</Field>
    </FileInfo> '
);

WITH ReplaceValue AS
(
    SELECT YourXMLColumn
          ,ca2.newSize
    FROM @dummy AS d
    CROSS APPLY(SELECT d.YourXMLColumn.value(N'(/FileInfo/Field[@Name="Size"]/text())[1]',N'int')) AS ca1(size)
    CROSS APPLY(SELECT CASE WHEN ca1.size % 1024=0 
                            THEN CAST(ca1.size/1024 AS VARCHAR(10)) + ' MB' 
                            ELSE CAST(ca1.size AS VARCHAR(10)) + ' KB' END) AS ca2(newSize)
)
UPDATE ReplaceValue SET YourXMLColumn.modify(N'replace value of (/FileInfo/Field[@Name="Size"]/text())[1] with sql:column("newSize")');

SELECT * FROM @dummy;

First I read the value of the "Size" field. If it is divideable by 1024 it will be written as "MB", otherwise the value remains as "KB".

The final UPDATE will update the CTE, but this affects the tables column actually. The SELECT shows the modified table data.