Passing a comma delimited list into XMLQuery - sql

Question

I am trying to pass a list of node names into my XMLQuery so I can delete all of the nodes except the ones in the list. When I hard code the list it works fine but when I pass it as an additional parameter it does not work...
This is the XML I am reading in:
<Activity>
<Math>
<ExpressionInteger2>7</ExpressionInteger2>
<ExpressionInteger3>1</ExpressionInteger3>
<ExpressionInteger4>5</ExpressionInteger4>
<ExpressionInteger0>1</ExpressionInteger0>
<ExpressionInteger1>1</ExpressionInteger1>
<ExpressionInteger6>-2</ExpressionInteger6>
<ExpressionInteger7>670000000</ExpressionInteger7>
</Math>
</Activity>
Then this is the query I am using to parse it where Activity.XMLData equal the XML and KeepFields holds the only node names I want to keep.
SELECT XMLQuery('copy $i := $p1
modify (delete node $i/Activity/Math/*[not(name()=($p2))])
return $i' PASSING BY VALUE XMLType(ActivityTable.XMLData) AS "p1", CAST(KeepList AS VARCHAR2(1000)) AS "p2" RETURNING CONTENT),
FROM ActivityTable
JOIN (SELECT VariableKey, '"' || LISTAGG(VariableName, '","') WITHIN GROUP (ORDER BY VariableName) || '"' AS KeepList
FROM KeepMathVariable
GROUP BY VariableKey) KeepFields ON KeepFields.VariableKey = ActivityTable.VariableKey
WHERE ActivityTable.VariableKey = 'DF6D6BB0-0BFF-4C9B-8251-374831DAD19E'
If I replace $p2 with the hard coded list "ExpressionInteger1","ExpressionInteger3" it will properly delete everything but those two nodes.
The result of the query should be :
<Activity>
<Math>
<ExpressionInteger3>1</ExpressionInteger3>
<ExpressionInteger1>1</ExpressionInteger1>
</Math>
</Activity>
This is the hardcoded working query:
SELECT XMLQuery('copy $i := $p1
modify (delete node $i/Activity/Math/*[not(name()=("ExpressionInteger1","ExpressionInteger3"))])
return $i' PASSING BY VALUE XMLType(ActivityTable.XMLData) AS "p1" RETURNING CONTENT),
FROM ActivityTable
WHERE ActivityTable.VariableKey = 'DF6D6BB0-0BFF-4C9B-8251-374831DAD19E'

Answer 1

When you put a variable into XQuery string, it is treated not as just replacement for some part of text, but as some atomic data. So providing a concatenated text that text is treated as a whole value and results in not what you wanted.
One possible way is to use tokenize() function to turn the string into array of strings right in XQuery.
with ActivityTable as (
/*base table with data*/
select '<Activity>
<Math>
<ExpressionInteger2>7</ExpressionInteger2>
<ExpressionInteger3>1</ExpressionInteger3>
<ExpressionInteger4>5</ExpressionInteger4>
<ExpressionInteger0>1</ExpressionInteger0>
<ExpressionInteger1>1</ExpressionInteger1>
<ExpressionInteger6>-2</ExpressionInteger6>
<ExpressionInteger7>670000000</ExpressionInteger7>
</Math>
</Activity>' as XMLData
, 1 as VariableKey
from dual
)
, KeepMathVariable as (
/*base table with keep variables*/
select 'ExpressionInteger1' as VariableName
, 1 as VariableKey
from dual
union all
select 'ExpressionInteger3', 1
from dual
)
, sep as (
/*separator for consistency in tokenize and listagg*/
select '#' as sep from dual
)
, KeepFields as (
/*build field list*/
select
v.VariableKey
, listagg(v.VariableName, s.sep) within group(order by 1) as KeepList
from KeepMathVariable v
cross join sep s
group by v.VariableKey, s.sep
)
select
/*Pretty-printing*/
XMLSerialize( content
/*Split separated list from KeepFields by separator into string array*/
XMLQuery('copy $i := $p1
modify (delete node $i/Activity/Math/*[not(name()=tokenize($p2, $p3))])
return $i'
PASSING BY value
XMLType(ActivityTable.XMLData) AS "p1",
KeepFields.KeepList as "p2",
s.sep as "p3"
RETURNING CONTENT
)
indent size = 2
) as res
from ActivityTable
join KeepFields
on ActivityTable.VariableKey = KeepFields.VariableKey
cross join sep s
| RES |
| :----------------------------------------------|
| <Activity> |
| <Math> |
| <ExpressionInteger3>1</ExpressionInteger3> |
| <ExpressionInteger1>1</ExpressionInteger1> |
| </Math> |
| </Activity> |
db<>fiddle here
Another option could be playing with passing collection type, but I didn't manage it to work.

Answer 2

I got it working with Tokenize
SELECT XMLQuery('copy $i := $p1
modify (delete node $i/Activity/Math/*[not(name()=(tokenize($p2)))])
return $i' PASSING BY VALUE XMLType(ActivityTable.XMLData) AS "p1", KeepList AS "p2" RETURNING CONTENT),
FROM ActivityTable
JOIN (SELECT LISTAGG(VariableName, ',') WITHIN GROUP (ORDER BY VariableName) AS KeepList
FROM KeepMathVariable
GROUP BY VariableKey) KeepFields ON KeepFields.VariableKey = ActivityTable.VariableKey
WHERE ActivityTable.VariableKey = 'DF6D6BB0-0BFF-4C9B-8251-374831DAD19E'