Oracle Error Message
PLS-00633: RETURN statement in a pipelined function cannot contain an expression
Reason for the Error
A RETURN statement in a pipelined function contains an expression, which is not allowed. Pipelined functions must send back values to the caller by using the PIPE statement.
Solution
Remove the expression from the RETURN statement and use a PIPE statement to return values. Else, convert the function into a non-pipelined function.