更新在数据库中存储为字符串的 XML 节点

Question

我可以了解将 XML 节点的值（每行不同）替换为新值（所有行通用）的 SQL 查询吗？

如果 XML 是：

<?xml version="1.0" encoding="utf-16"?>
<EmployeeDetail xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Name>MyName</Name>
  <Age>20</Age>
  <Salary>15000</Salary>
</EmployeeDetail>

我需要将所有 XML 列的 <Salary>DifferingSalary</Salary> 更新为 <Salary>10000</Salary>

试过了：

DECLARE @salary VARCHAR(10) = '10000';

UPDATE TABLE_NAME
SET [COLUMN_NAME].modify('replace value of 
    (/EmployeeDetail/Salary/text())[1] 
    with (sql:variable("@salary"))
');

输出：

无法调用 nvarchar(max) 上的方法。

注意：XML 以字符串形式存储在数据库中。

提前致谢！

Answer 1

您可以尝试以下方法。

它展示了如何在以下情况下修改<salary>元素值：

• xmldata 列是 XML 数据类型。
• xmldata 列是 NVARCHAR(MAX) 数据类型。

SQL #1

-- DDL and sample data population, start
DECLARE @tbl TABLE (ID INT IDENTITY PRIMARY KEY, xmldata XML);
INSERT INTO @tbl ( xmldata) VALUES
(N'<?xml version="1.0" encoding="utf-16"?>
<EmployeeDetail xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <Name>MyName</Name>
    <Age>20</Age>
    <Salary>15000</Salary>
</EmployeeDetail>');
-- DDL and sample data population, end

-- before
SELECT * FROM @tbl;

DECLARE @salary VARCHAR(10) = '10000';

UPDATE @tbl
SET xmldata.modify('replace value of 
    (/EmployeeDetail/Salary/text())[1] 
    with (sql:variable("@salary"))
');

-- after
SELECT * FROM @tbl;

SQL #2

-- DDL and sample data population, start
DECLARE @tbl TABLE (ID INT IDENTITY PRIMARY KEY, xmldata NVARCHAR(MAX));
INSERT INTO @tbl ( xmldata) VALUES
(N'<?xml version="1.0" encoding="utf-16"?>
<EmployeeDetail xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <Name>MyName</Name>
    <Age>20</Age>
    <Salary>15000</Salary>
</EmployeeDetail>');

DECLARE @realXML TABLE (ID INT, realXML XML);
-- DDL and sample data population, end

-- populate temporary table
INSERT INTO @realXML
SELECT ID, cast(xmldata AS XML)
FROM @tbl;

DECLARE @salary VARCHAR(10) = '10000';

/*
Unfortunately, we can not assign from a xml.modify() statement. 
Modify works on a variable and a column only. 
Also, we cannot use modify on a CAST().
*/
-- update temporary table
UPDATE @realXML
SET realXML.modify('replace value of 
            (/EmployeeDetail/Salary/text())[1] 
            with (sql:variable("@salary"))
        ');

-- update real table 
UPDATE tbl
SET xmldata = CAST(t.realXML AS NVARCHAR(MAX))
FROM @realXML AS t INNER JOIN @tbl AS tbl
ON tbl.ID = t.ID;