How to search XML in SQL Server - sql

Question

I looked at some threads but I think I'm missing something in Microsoft SQL Server (SSMS).
I have XML in column defined as XML datatype that looks like this:
(I erased stuff before this not sure if it's needed)
<ItemGroupData ItemGroupOID="TEST" TransactionType="Insert">
<ItemData ItemOID="TEACHER" Value="145"/>
<ItemData ItemOID="AGE" Value="50" />
</ItemGroupData>
<ItemGroupData ItemGroupOID="TEST" TransactionType="Insert">
<ItemData ItemOID="TEACHER" Value="151"/>
<ItemData ItemOID="AGE" Value="42" />
</ItemGroupData>
There's stuff I truncated but what is the most optimal way to locate the XML file where teacher 145 is and they can be in any of the Itemdata groups?
I can find it like:
SELECT
CAST(XML AS nvarchar(max)) AS test
FROM
table1
WHERE
XML LIKE '%14%'
but I am looking into learning different ways without casting unless that is the most optimal way?

Answer 1

Yes, that "stuff before" that you erased will be very important! You need to build up XPath expressions to select individual pieces from the XML - and those depend on everything from the root on down! Also - you might have XML namespaces that are defined in the "stuff before" - which you need to respect to get any results.
Anyhoo - ASSUMING you have just a <root>....</root> node before your XML, you could get your desired result like this :
DECLARE #XmlTbl TABLE (ID INT NOT NULL, XmlData XML)
INSERT INTO #XmlTbl (ID, XmlData)
VALUES (1,
'<root><ItemGroupData ItemGroupOID="TEST" TransactionType="Insert">
<ItemData ItemOID="TEACHER" Value="145"/>
<ItemData ItemOID="AGE" Value="50" />
</ItemGroupData>
<ItemGroupData ItemGroupOID="TEST" TransactionType="Insert">
<ItemData ItemOID="TEACHER" Value="151"/>
<ItemData ItemOID="AGE" Value="42" />
</ItemGroupData></root>')
SELECT
t.ID,
XC.value('(#ItemGroupOID)', 'varchaR(50)') AS ItemGroupOID,
XC.value('(#TransactionType)', 'varchaR(50)') AS TransactionType,
XC2.value('#ItemOID', 'varchar(25)') AS ItemOID,
XC2.value('#Value', 'int') AS value
FROM
#XmlTbl t
CROSS APPLY -- "enumerate" the <ItemGroupData> nodes under <root>
XmlData.nodes('/root/ItemGroupData') AS XT(XC)
CROSS APPLY -- "enumerate" the <ItemData> subnodes
XC.nodes('ItemData') AS XT2(XC2)
WHERE
XC.value('(ItemData/#Value)[1]', 'int') = 145
This would return these results:
ID
ItemGroupOID
TransactionType
ItemOID
value
1
TEST
Insert
TEACHER
145
1
TEST
Insert
AGE
50

Answer 2

SQL Server supports powerful XQuery language to deal with the XML data type.
Please try the following solution.
It is using XPath predicate [#Value=sql:variable("#TeacherValue")] to search directly in the XML data type.
The sql:variable("#TeacherValue") construct allows to pass a parameter to it.
Also, SQL Server supports XML indexes for that.
SQL
-- DDL and sample data population, start
DECLARE #tbl TABLE (ID INT IDENTITY PRIMARY KEY, XmlData XML);
INSERT INTO #tbl (XmlData) VALUES
(N'<root>
<ItemGroupData ItemGroupOID="TEST" TransactionType="Insert">
<ItemData ItemOID="TEACHER" Value="145"/>
<ItemData ItemOID="AGE" Value="50"/>
</ItemGroupData>
<ItemGroupData ItemGroupOID="TEST" TransactionType="Insert">
<ItemData ItemOID="TEACHER" Value="151"/>
<ItemData ItemOID="AGE" Value="42"/>
</ItemGroupData>
</root>');
-- DDL and sample data population, end
DECLARE #TeacherValue INT = 145;
SELECT t.ID
, p.value('#ItemGroupOID', 'VARCHAR(50)') AS ItemGroupOID
, p.value('#TransactionType', 'VARCHAR(50)') AS TransactionType
, c.value('#ItemOID', 'VARCHAR(25)') AS ItemOID
, c.value('#Value', 'INT') AS value
FROM #tbl AS t
CROSS APPLY XmlData.nodes('/root/ItemGroupData[ItemData[#ItemOID="TEACHER"
and #Value=sql:variable("#TeacherValue")]]') AS t1(p)
CROSS APPLY t1.p.nodes('ItemData') AS t2(c);
Output
ID
ItemGroupOID
TransactionType
ItemOID
value
1
TEST
Insert
TEACHER
145
1
TEST
Insert
AGE
50