Oracle function Select Into not working correctly - oracle

Question

Hi all i have the code below :
CREATE OR REPLACE FUNCTION GET_STATE_USER (user_id IN NUMBER)
RETURN VARCHAR2
AS
staffName VARCHAR2 (50);
BEGIN
DBMS_OUTPUT.put_line(user_id);
SELECT bs.FIRST_NAME || ' ' || bs.LAST_NAME
INTO staffName
FROM EMPLOYEE e
WHERE bs.USER_ID = user_id;
RETURN (CASE
WHEN staffName IS NOT NULL THEN staffName
ELSE 'Invalid'
END);
END;
/
And I'm getting following error :
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at "GET_STATE_USER", line 8

Answer 1

You must change the name of the input variable. The variable name must not be the same as the table column name.
try this :
CREATE OR REPLACE NONEDITIONABLE FUNCTION GET_STATE_USER (user__id IN NUMBER)
RETURN VARCHAR2
AS
staffName VARCHAR2 (50);
BEGIN
DBMS_OUTPUT.put_line(user__id);
SELECT bs.FIRST_NAME || ' ' || bs.LAST_NAME
INTO staffName
FROM EMPLOYEE bs
WHERE bs.USER_ID = user__id;
RETURN (CASE
WHEN staffName IS NOT NULL THEN staffName
ELSE 'Invalid'
END);
END;

Answer 2

Actually I wanted to check two tables for existence of a record and finally the code below did the trick :
CREATE OR REPLACE FUNCTION GET_STATE_USER (userId IN NUMBER)
RETURN VARCHAR2
AS
r_count NUMBER;
userTitle VARCHAR2 (100);
BEGIN
SELECT COUNT (1)
INTO r_count
FROM EMPLOYEE bs
WHERE bs.USER_ID = userId;
IF r_count > 0
THEN
SELECT bs.FIRST_NAME || ' ' || bs.LAST_NAME
INTO userTitle
FROM EMPLOYEE bs
WHERE bs.USER_ID = userId;
ELSE
SELECT ac.name
INTO userTitle
FROM allcustomer ac
WHERE ac.CUSTOMER_USER_ID = userId;
END IF;
RETURN (CASE
WHEN userTitle IS NOT NULL THEN userTitle
ELSE 'inavlid'
END);
END;
/