SQL XQuery - XML 数据类型方法 "modify" 的参数 1 必须是字符串文字

Question

我有以下 SQL 的片段：

declare @idx int = 1

while (@idx <= @NumThresholds)
begin
    declare @strIdx nvarchar(100) = convert(varchar(100), @idx)
    declare @xqueryString nvarchar(max) = concat('replace value of (//*:ElecTariffElements/*:ThresholdMatrix/*:Thresholds/*:BlockThreshold/text())[', @strIdx, '] with "0"')
    set @xml.modify(@xqueryString)
    set @idx = @idx + 1
end

我想更新 BlockThreshold 元素的每个值。

但是我收到错误：

The argument 1 of the XML data type method "modify" must be a string literal.

我也试过像这样使用 sql:variable("@strIdx"):

declare @idx int = 1

while (@idx <= @NumThresholds)
begin
    declare @strIdx nvarchar(100) = convert(varchar(100), @idx)
    set @xml.modify('replace value of (//*:ElecTariffElements/*:ThresholdMatrix/*:Thresholds/*:BlockThreshold/text())[sql:variable("@strIdx")] with "0"')
    set @idx = @idx + 1
end

但是这之后我得到了这个错误：

XQuery [modify()]: Only 'http://www.w3.org/2001/XMLSchema#decimal?', 'http://www.w3.org/2001/XMLSchema#boolean?' or 'node()*' expressions allowed as predicates, found 'xs:string ?'

我只想遍历元素并替换值，但这似乎比我预期的要困难得多。

非常感谢任何帮助！

Answer 1

declare @xml xml = N'
<ElecTariffElements>
<ThresholdMatrix>
<Thresholds>
<BlockThreshold>1</BlockThreshold>
<BlockThreshold>2</BlockThreshold>
<BlockThreshold>3</BlockThreshold>
<BlockThreshold>4</BlockThreshold>
<BlockThreshold>4</BlockThreshold>
</Thresholds>
</ThresholdMatrix>
</ElecTariffElements>
';


declare @idx int = 1;
declare @NumThresholds int = @xml.value('count(//*:ElecTariffElements/*:ThresholdMatrix/*:Thresholds/*:BlockThreshold)', 'int');
select @NumThresholds, @xml;

while (@idx <= @NumThresholds)
begin
    set @xml.modify('replace value of (//*:ElecTariffElements/*:ThresholdMatrix/*:Thresholds/*:BlockThreshold/text())[sql:variable("@idx")][1] with 0');
    select @xml;
    set @idx = @idx + 1;
end

select @xml;

SQL XQuery - XML 数据类型方法 "modify" 的参数 1 必须是字符串文字

SQL XQuery - The argument 1 of the XML data type method "modify" must be a string literal

sql-server

xquery

string-literals