How to build dynamic Xquery

Hello

I am trying to use the xml.query() method to output xml. Is there any way of storing the xqueries themselves in the database?

This works:

SELECT Col.query('
<Root>
<Header>
{
for $e in Report/PolicyBatchRef
return $e/PolicyBatchRef
}
</Header>
<NewElement>
{
for $e in Report/PolicyBatchRef/Locations/Location
return $e
}
</NewElement>
</Root>
')
FROM xmltest where id = 1

but this doesn't:

declare @.xquery nvarchar(max)
set @.xquery = '<Root>
<Header>
{
for $e in Report/PolicyBatchRef
return $e/PolicyBatchRef
}
</Header>
<NewElement>
{
for $e in Report/PolicyBatchRef/Locations/Location
return $e
}
</NewElement>
</Root>'
SELECT col.query(@.xquery) from xmltest where id = 1

I get the error

Msg 8172, Level 16, State 1, Line 4
The argument 1 of the xml data type method "query" must be a string literal.

Same thing happens when I store the xquery in the DB.

Any ideas?

Thanks very much

The string argument to the query function must be a string literal, so you cannot pass it in as a parameter. You have a few options:

1. Create UDF's that encapsulate the SELECT and the xquery, and invoke these.

2. Store strings that represent the SELECT and the xquery and invoke them at runtime using sp_executesql

3. store the strings that represent the xquery and combine them with the strings for the SELECT statement, and execute with sp_executesql. This has the most potential for SQL injection since you are constructing SQL dynamically with string concatenation. This method should be used only if the other two ways cannot be used.

|||

You can dynamically create XPath queries using sql variables.

I have successfully used something like

declare @.Date varchar(10)

set @.Date = replace(convert(varchar(10), getdate(), 121), '-', '')

WITH XMLNAMESPACES( 'https://www,somewhere.com/Bureau' AS "Bureau")

SELECT

AggDefaultAmount = convert(varchar(50), ResponseXML.query('sum(/BureauResponse/Bureau:ND07/Bureau:ND07/Bureau:Amount[../Bureau:InformationDate<sql:variable("@.Date")])'))

FROM

DB..testxml WITH (NOLOCK)

Adapt adopt and improve.

|||

Hi,

I need to a have a Store procedure that takes xml as input and it stores in my database tables. Using the nodes() method and value() method, I am able to solve this but only issue I have is these methods take arguments only as string literals. So, I have to hard code the xquery in the SP. I expect to read the xquery from a table and fetch it in a variable within the SP and pass it as the parameter to the Value() and nodes() method.

Please advice.

Sample code I have as below

declare @.xmldoc xml

SET @.xmldoc = '<customer><name>John</name><city>New York</city></customer>'

--This select works

SELECT

T.C.value('name[1]',varchar(50))

T.C.value('city[1]',varchar(50))

FROM @.xmldoc.nodes('/customer') AS T(C)

--But this does not work when I try to specify xquery using a variable as below

declare @.xquery_name varchar(100),@.xquery_city varchar(100), @.xquery_cust varchar(100)

SELECT @.xquery_name = 'name[1]', @.xquery_city = 'city[1]', @.xquery_cust = '/customer'

SELECT

T.C.value(@.xquery_name ,varchar(50))

T.C.value('@.xquery_city',varchar(50))

FROM @.xmldoc.nodes(@.xquery_cust) AS T(C)

Please help me out.