XPATH Get list item with ID held in sibling - sql-server

Question

Using XPath in T-SQL I am trying to get an attribute value from the options list where the Id to choose the right list item is found in the Value element.
Any help would be appreciated.
declare #myTable table (pk int primary key identity(1,1), myXML xml)
insert into #myTable values ('
<Fields>
<Field ID="1111">
<Description>How Now Brown Cow</Description>
<Value>3</Value>
<Options>
<Options>
<Option OptionContent="Select one" OptionID="-1" />
<Option OptionContent="Mars" OptionID="1" />
<Option OptionContent="Pluto" OptionID="2" />
<Option OptionContent="Saturn" OptionID="3" />
</Options>
</Options>
</Field>
<Field ID="2222">
<Description>Foo Bar</Description>
<Value>2</Value>
<Options>
<Options>
<Option OptionContent="Select one" OptionID="-1" />
<Option OptionContent="Coffee" OptionID="1" />
<Option OptionContent="Tea" OptionID="2" />
<Option OptionContent="Water" OptionID="3" />
<Option OptionContent="Juice" OptionID="4" />
<Option OptionContent="Water" OptionID="5" />
</Options>
</Options>
</Field>
</Fields>
')
select
myField.ref.value('#ID', 'smallint') as [ID]
,myField.ref.value('(./Description)[1]', 'nvarchar(10)') as [Description]
,myField.ref.value('(./Value)[1]', 'int') as [Value]
,myField.ref.value('(./Options/Options/Option[#OptionID="-1"]/#OptionContent)[1]', 'nvarchar(10)') as [SelectedDescription]
from #myTable c
cross apply c.myXML.nodes('/Fields/Field') myField(ref)
ID Description Value Actual Expected
------ ----------- ----------- ---------- --------
1111 How Now Br 3 NULL Saturn
2222 Foo Bar 2 NULL Tea

Answer 1

Change
(./Options/Options/Option[#OptionID="-1"]/#OptionContent)[1]
to
let $id := ./Value[1] return (./Options/Options/Option[#OptionID=$id]/#OptionContent)[1]
So your query should be
select
myField.ref.value('#ID', 'smallint') as [ID]
,myField.ref.value('(./Description)[1]', 'nvarchar(10)') as [Description]
,myField.ref.value('(./Value)[1]', 'int') as [Value]
,myField.ref.value('let $id := ./Value[1] return (./Options/Options/Option[#OptionID=$id]/#OptionContent)[1]', 'nvarchar(10)') as [SelectedDescription]
from #myTable c
cross apply c.myXML.nodes('/Fields/Field') myField(ref)