CODEWITHSUNDEEP
sql-serverxmlxquery
jpsnow72
jpsnow72

Reputation: 995

Update SQL Server table with XML

I have an XML variable that looks like this:

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

</IDs>
</code>

I want to use that in a stored procedure (SQL Server) that will update a table.

My table look like this:

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

The statement should increase the letter value associated with the id.

SO it would look like this:

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.

This is what I have so far - (The second line is where i need the most help.):

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

Upvotes: 4

Views: 10388

Answers (3)

wBob
wBob

Reputation: 14389

One dynamic SQL solution. Not too pretty but totally dynamic:

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

Upvotes: 0

user610217
user610217

Reputation:

I would suggest you change your XML to resemble this:

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

With this format, you can write a query like so:

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;

You can then add these to a table as necessary, but the table you designed doesn't look like it would be very useful.

Upvotes: 0

marc_s
marc_s

Reputation: 755321

You would have to do something along the lines of this:

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

This will do it - but it's really quite ugly. The main problem is: you cannot get the column name as a value from somewhere else, to use it in the UPDATE statement - unless you go the dynamic SQL route, which has its own set of pros and cons and can get rather messy.

If you're interested in dynamic SQL - The Curse and Blessings of Dynamic SQL by Erland Sommarskog is an absolute must-read - read it before you launch into using dynamic SQL!

Upvotes: 3

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