Question

我有一个XML变量，如下所示：

<code>
<IDs>
    <ID id="1">a</ID>
    <ID id="43">d</ID>
    <ID id="3">b</ID>

</IDs>
</code>

我想在将更新表的存储过程（SQL Server）中使用它。

我的表格如下：

ID INT,
a INT,
b INT,
c INT,
d INT

该语句应增加与id相关联的字母值。

所以看起来像这样：

Table Row with ID = 1, update column "a" by increasing the current value by 1.
Table Row with ID = 43 - update column "d" by increasing current value by 1.
Finally Table row with ID= 3 - update column "b" by increasing value by 1.

这就是我到目前为止 - （第二行是我需要最多帮助的地方。）：

Update MyTable
SET @letter = letterVal +1
WHERE ID IN(
SELECT x.v.value('@id','INT')
FROM @xmlIDs.nodes('/IDs/ID') x(v)
)

Answer 1

你必须按照以下方式做点什么：

DECLARE @input XML = '<code>
<IDs>
    <ID id="1">a</ID>
    <ID id="43">d</ID>
    <ID id="3">b</ID>

</IDs>
</code>'

;WITH ParsedXML AS
(
SELECT
    ID = C.value('(@id)[1]', 'int'),
    ColumnName = C.value('(.)[1]', 'varchar(10)')
FROM @Input.nodes('/code/IDs/ID') AS T(C)
)
UPDATE MyTable 
SET a = CASE WHEN p.ColumnName = 'a' THEN t.a + 1 ELSE t.a END,
    b = CASE WHEN p.ColumnName = 'b' THEN t.b + 1 ELSE t.b END,
    c = CASE WHEN p.ColumnName = 'c' THEN t.c + 1 ELSE t.c END,
    d = CASE WHEN p.ColumnName = 'd' THEN t.d + 1 ELSE t.d END
FROM MyTable t
INNER JOIN ParsedXml p ON t.ID = p.ID

SELECT * FROM Mytable

这样做会 - 但它真的很难看。主要问题是：你不能从其他地方获取列名作为值，在UPDATE语句中使用它 - 除非你去动态SQL路由，它有自己的优点和缺点，可以得到相当混乱。

如果您对动态SQL感兴趣 - Erland Sommarskog的The Curse and Blessings of Dynamic SQL是绝对必读 - 在之前阅读，您开始使用动态SQL ！

Answer 2

我建议您将XML更改为类似于：

<questions>
    <question id="1" answer="a" />
    <question id="43" answer="d" />
    <question id="3" answer="b" />
</questions>

使用此格式，您可以编写如下查询：

with CTE as (
    select
         x.n.value('@answer', 'char(1)') as answer
    from
        @Input.nodes('//questions/question') as x(n)
)
select 
    answer,
    count(answer) as answerCount
from
    CTE
group by
    answer;

然后，您可以根据需要将这些添加到表中，但您设计的表看起来不太有用。

Answer 3

一种动态SQL解决方案。不太漂亮，但完全充满活力：

IF OBJECT_ID('tempdb..#tmp') IS NOT NULL DROP TABLE #tmp
GO
CREATE TABLE #tmp ( ID INT, a INT, b INT, c INT, d INT )
GO

INSERT INTO #tmp VALUES
    ( 1, 0, NULL, NULL, NULL ),
    ( 43, NULL, NULL, NULL, 0 ),
    ( 3, NULL, 0, NULL, NULL )
GO

SELECT 'before' s, * FROM #tmp

DECLARE @xml XML

SET @xml = '<code>
  <IDs>
    <ID id="1">a</ID>
    <ID id="43">d</ID>
    <ID id="3">b</ID>
  </IDs>
</code>'


-- Run a cursor through the XML resultset to update the table
DECLARE update_cursor CURSOR FAST_FORWARD LOCAL FOR 
SELECT
    x.y.value('@id', 'INT') id,
    x.y.value('.', 'VARCHAR(50)') columnName
FROM @xml.nodes('code/IDs/ID') AS x(y)

-- Cursor variables
DECLARE @id INT, @columnName VARCHAR(50)
DECLARE @sql NVARCHAR(MAX)

OPEN update_cursor

FETCH NEXT FROM update_cursor INTO @id, @columnName
WHILE @@fetch_status = 0
BEGIN

    --SELECT @id, @columnName

    SET @sql = 'UPDATE #tmp SET ' + @columnName + ' += 1 WHERE ID = ' + CAST( @id AS VARCHAR(20) )

    EXEC(@sql)
    --SELECT @sql

    FETCH NEXT FROM update_cursor INTO @id, @columnName
END

CLOSE update_cursor
DEALLOCATE update_cursor
GO

SELECT 'after' s, * FROM #tmp

使用XML更新SQL Server表

3 个答案: