[英]How to insert an attribute into xml data which is saved as nvarchar(max)
[英]How to parse XML encoded as UTF-8 from a NVARCHAR(MAX) attribute?
我在解析存儲在NVARCHAR(MAX)
類型字段中的XML字符串時遇到問題(我無法更改此字段的類型)。
這是我的桌子(WorkingHours):
CREATE TABLE WorkingHours(
[ID] [int] NOT NULL PRIMARY KEY,
[CONTENT] [nvarchar](MAX) NOT NULL,
-- ...
);
以下是[CONTENT]
屬性的示例:
<?xml version="1.0" encoding="UTF-8"?>
<calendar>
<day number="1" worked_day="no">
<interval number="1" begin_hour="08:30" end_hour="12:00"/>
<interval number="2" begin_hour="13:30" end_hour="17:00"/>
<interval number="3" begin_hour="" end_hour=""/></day>
<day number="2" worked_day="no">
<interval number="1" begin_hour="08:30" end_hour="12:00"/>
<interval number="2" begin_hour="13:30" end_hour="17:00"/>
<interval number="3" begin_hour="" end_hour=""/>
</day>
<day number="3" worked_day="no">
<interval number="1" begin_hour="08:30" end_hour="12:00"/>
<interval number="2" begin_hour="13:30" end_hour="17:00"/>
<interval number="3" begin_hour="" end_hour=""/>
</day>
<day number="4" worked_day="no">
<interval number="1" begin_hour="08:30" end_hour="12:00"/>
<interval number="2" begin_hour="13:30" end_hour="17:00"/>
<interval number="3" begin_hour="" end_hour=""/>
</day>
<day number="5" worked_day="no">
<interval number="1" begin_hour="08:30" end_hour="12:00"/>
<interval number="2" begin_hour="13:30" end_hour="17:00"/>
<interval number="3" begin_hour="" end_hour=""/>
</day>
<day number="6" worked_day="no">
<interval number="1" begin_hour="" end_hour=""/>
<interval number="2" begin_hour="" end_hour=""/>
<interval number="3" begin_hour="" end_hour=""/>
</day>
<day number="7" worked_day="no">
<interval number="1" begin_hour="" end_hour=""/>
<interval number="2" begin_hour="" end_hour=""/>
<interval number="3" begin_hour="" end_hour=""/>
</day>
</calendar>
如您所見,數據編碼為UTF-8 。
現在,我想解析這些數據以創建一些計算:
DECLARE @RawContent [nvarchar](MAX) = (
SELECT wh.[CONTENT]
FROM [WorkingHours] wh
WHERE wh.[ID] = 100);
DECLARE @XMLContent [Xml] = @RawContent; // KO
-- DECLARE @XMLContent [Xml] = CAST(@RawContent AS XML); // KO
-- DECLARE @XMLContent [Xml] = CONVERT(XML, @RawContent); // KO
-- Just a test to query XML data.
SELECT
C.WD.value('@number', 'int') AS DayId
FROM @XMLContent.nodes('/calendar/day') AS C(WD);
我不知道如何將結果(包含UTF-8 XML字符串的nvarchar(max)字段)轉換為XML值。 SQL Server返回以下錯誤:
"Unable to switch encoding"
它指的是CAST行(當我定義@XMLContent變量時)。
有什么想法解決這個問題?
刪除處理指令 - 它沒有意義且不正確,因為數據已經以UTF-16編碼(因為它存儲為NVARCHAR
)。 如果您無法更改已存在的數據,則必須依賴(略微脆弱)字符串替換:
CAST(REPLACE(wh.[CONTENT], '<?xml version="1.0" encoding="UTF-8"?>', '') AS XML)
請注意,顯式指示編碼是UTF-16也可以工作 - 雖然它什么都不添加。
另一種選擇是首先轉換為VARCHAR
數據類型 - 非Unicode - 然后轉換為XML
:
DECLARE @RawContent [nvarchar](MAX) = (
SELECT wh.[CONTENT]
FROM [WorkingHours] wh
WHERE wh.[ID] = 100);
DECLARE @XMLContent XML = CAST(CAST(@RawContent AS VARCHAR(MAX)) AS XML)
-- Just a test to query XML data.
SELECT
C.WD.value('@number', 'int') AS DayId
FROM @XMLContent.nodes('/calendar/day') AS C(WD);
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