如何在ntext列上使用modify方法而不将列类型更改为xml使用CAST或CONVERT或其他方法

问题描述

我需要更新存储在ntext列的data列中的XML内容中的两个属性

我尝试在xml.modify列上使用CAST或CONVERT的{​​{1}} XQuery方法，但没有成功：

尝试使用data

CAST

我收到此错误

UPDATE [dbo].[CodeSystemCodes_data] 
    SET
        (CAST([data] as xml)).modify('replace value of (/Utilities.CodeSystems.CodeSystemCodes/@Description)[1] with sql:variable("@NEW_EXAM_NAME")')
    WHERE [data] like '%' + @CURRENT_EXAM_CODE + '%'

...在CAST之前，删除'（'也会失败

我最终创建了一个临时表，该表具有单个Incorrect syntax near '(' 类型的列，名为XML，该列使用该表上的Modify方法，然后将数据返回到原始表中，但这似乎太过夸张了>

如何使用xmlData类型的modify列使用data方法而不使用任何中间表？也许使用CAST或CONVERT或其他方式。我尝试使用XML变量也没有成功。

请记住，由于我不是DBA或负责决策的人，因此目前无法更改列类型。

我使用XML修改方法而不是REPLACE，因为我不想对XML数据进行错误的替换。

还有其他类似的问题，但目前都无法回答

• How to update XML in ntext column?

• Inserting data to ntext xml column (Cannot call methods on ntext error)

代码：

ntext

解决方法

不幸的是，您所做的事情与将XML存储为文本时的操作差不多。

如果要摆脱使用临时表的麻烦，可以尝试这样的操作。您可以在SSMS中运行它。

/* Base table mock-up */
DECLARE @Data TABLE ( [data] NTEXT,[id] INT IDENTITY (1,1) );
INSERT INTO @Data ( [data] ) VALUES 
    ( '<root><values><val>Value 1</val><val>to_be_changed</val></values></root>' ),( '<root><values><val>All is well here.</val><val>All is well here,too.</val></values></root>' ),( '<root><values><val>Another value.</val><val>to_be_changed</val></values></root>' );

/* Find/Replace variables */
DECLARE 
    @find_value VARCHAR(50) = 'to_be_changed',@replace_value VARCHAR(50) = 'Value 2';

/* Create a table variable to temporarily house the ntext data as xml so the XML may be modified */
DECLARE @Temp TABLE ( DataXml XML,id INT );

/* Insert [data] into the XML column */
INSERT INTO @Temp ( DataXml,[id] )
SELECT CAST ( [data] AS XML ),[id] FROM @Data WHERE [data] LIKE '%' + @find_value + '%';

/* Show the @Data resultset before modifying */
SELECT * FROM @Data;

/* The WHILE is to make sure every node that requires updating gets updated */
/* Modify each instance matching the @find_value criteria */
WHILE EXISTS ( SELECT * FROM @Temp WHERE DataXml.exist( '//root/values/val/text()[.=sql:variable("@find_value")]' ) = 1 )
UPDATE @Temp
SET
    DataXml.modify ('
        replace value of (/root/values/val/text()[.=sql:variable("@find_value")])[1]
        with sql:variable("@replace_value")
    ');

/* Update the results back to the ntext column */
UPDATE @Data
SET
    [data] = CAST ( t.DataXml AS NVARCHAR(MAX) )
FROM @Data d
INNER JOIN @Temp t
    ON d.id = t.id;

/* Show the updated @Data resultset */
SELECT * FROM @Data;

@Data的初始选择：

/* Show the @Data resultset before modifying */
SELECT * FROM @Data;

返回

+---------------------------------------------------------------------------------------------+----+
|                                            data                                             | id |
+---------------------------------------------------------------------------------------------+----+
| <root><values><val>Value 1</val><val>to_be_changed</val></values></root>                    |  1 |
| <root><values><val>All is well here.</val><val>All is well here,too.</val></values></root> |  2 |
| <root><values><val>Another value.</val><val>to_be_changed</val></values></root>             |  3 |
+---------------------------------------------------------------------------------------------+----+

@Data的最终结果集：

/* Show the updated @Data resultset */
SELECT * FROM @Data;

返回

+---------------------------------------------------------------------------------------------+----+
|                                            data                                             | id |
+---------------------------------------------------------------------------------------------+----+
| <root><values><val>Value 1</val><val>Value 2</val></values></root>                          |  1 |
| <root><values><val>All is well here.</val><val>All is well here,too.</val></values></root> |  2 |
| <root><values><val>Another value.</val><val>Value 2</val></values></root>                   |  3 |
+---------------------------------------------------------------------------------------------+----+

可能的替代方法： 也许是您的文字上的简单REPLACE。

UPDATE @Data
SET
    [data] = REPLACE ( CAST ( [data] AS NVARCHAR(MAX) ),@find_value,@replace_value )
FROM @Data d
WHERE
    d.[data] LIKE '%' + @find_value + '%';

更新：

我应该更清楚地说“我不想使用任何中间表”

/* For-each find/replace instance found... */
WHILE EXISTS ( SELECT * FROM @Data WHERE CAST ( [data] AS XML ).exist( '//root/values/val/text()[.=sql:variable("@find_value")]' ) = 1 )
BEGIN

    DECLARE @id INT,@xml XML;
    SELECT TOP 1
        @id = id,@xml = CAST ( [data] AS XML )
    FROM @Data
    WHERE CAST ( [data] AS XML ).exist( '//root/values/val/text()[.=sql:variable("@find_value")]' ) = 1;

    -- Modify the XML --
    SET @xml.modify('
        replace value of (/root/values/val/text()[.=sql:variable("@find_value")])[1]
        with sql:variable("@replace_value")
    ');

    -- Update the modified XML --
    UPDATE @Data
    SET
        [data] = CAST ( @xml AS NVARCHAR(MAX) )
    WHERE id = @id;

END

/* Show the updated resultset */
SELECT * FROM @Data ORDER BY id;

更新的结果集：

+---------------------------------------------------------------------------------------------+----+
|                                            data                                             | id |
+---------------------------------------------------------------------------------------------+----+
| <root><values><val>Value 1</val><val>Value 2</val><val>Value 2</val></values></root>        |  1 |
| <root><values><val>All is well here.</val><val>All is well here,too.</val></values></root> |  2 |
| <root><values><val>Another value.</val><val>Value 2</val></values></root>                   |  3 |
+---------------------------------------------------------------------------------------------+----+

按OP更新

感谢您的最后一个解决方案，我最终完成了此操作，无需进行while循环

DECLARE @CURRENT_EXAM_CODE NVARCHAR(10) = 'BXC_14B'
DECLARE @NEW_EXAM_NAME NVARCHAR(10) = 'BCC'
DECLARE @CODE_DESC NVARCHAR(50)
DECLARE @XML_DATA XML


-- convert existing NTEXT data into XML
SELECT @XML_DATA =
    CAST([data] as xml)
    FROM [dbo].[CodeSystemCodes_data]   
    WHERE [data] like '%' + @CURRENT_EXAM_CODE + '%'

-- update the xml data
SET @XML_DATA.modify('replace value of (/Utilities.CodeSystems.CodeSystemCodes/@Description)[1] with sql:variable("@NEW_EXAM_NAME")')

SET @CODE_DESC = @CURRENT_EXAM_CODE + ' - ' + @NEW_EXAM_NAME

SET @XML_DATA.modify('replace value of (/Utilities.CodeSystems.CodeSystemCodes/@CodeAndDescription)[1] with sql:variable("@CODE_DESC")')

-- convert xml data back to ntext type
UPDATE [dbo].[CodeSystemCodes_data] 
    SET 
        [data] = CAST(CAST(@XML_DATA as nvarchar(max)) as ntext)
    WHERE [data] like '%' + @CURRENT_EXAM_CODE + '%'