Message Oracle PLS-00513 - PL/SQL function called from SQL must return value of legal SQL type

ERRORPL/SQL function called from SQL must return value of legal SQL type
CAUSEIn a SQL statement, do not call a PL/SQL function having a return type that can not be handled by SQL. For example, type BOOLIAN, records and indexed-tables are not supported by SQL and functions returneing such values can not be called from SQL.
ACTIONNone