ORA-42647
Missing '_id' field at the root level for JSON-relational duality view 'string'.
Cause
The '_id' field is missing from the root level of JSON-relational duality view definition. A duality view must always have '_id' as a field at the root level which captures the value of the primary key columns.
Action
Add '_id' at the root level of the duality view definition to capture the primary key column for JSON-relational duality view. Refer to Oracle documentation for duality view syntax and examples.