خطأ يظهرلى فى جملة Sql

[جيتارا]

السلام عليكم

قمت بكتابة كود لتحويل جملة select الى صيغة xml
ولكن يظهر لى خطأ ora-00913 too many values
وهاهو الكود...

select xmlelement(
"xml",
xmlagg(xmlelement(
"region",
xmlattributes(p.area_id as "region"),
xmlagg(xmlelement(
"area_type",
xmlattributes(p.area_type as "area_type"),
(select xmlagg(xmlelement(
"product",
xmlattributes(c.name as "name",
pr.description_arabic as "description"))),
xmlagg(xmlelement(
"customer_licenses",
xmlattributes(cl.position_id as "pos_id",
cl.area as "area",
cl.description as "position",
cl.start_date as "start_date",
cl.end_date as "end_date",
cl.notes as "notes")))




FROM customer_licenses cl
LEFT JOIN positions p
ON (cl.position_id=p.id)
LEFT JOIN products pr
ON (cl.product_type=pr.id)
LEFT JOIN customers c
ON(c.id=cl.cust_id)
WHERE cl. license_type_id=4
and p.area_id IS NOT NULL
AND p.area_type IS NOT NULL
and p.id=cl.position_id
group by cl.position_id
)

)
)
)
)
)
xml
FROM positions p
WHERE p.area_id IS NOT NULL AND p.area_type IS NOT NULL
group by p.area_id

;

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