Why does this basic 'Select Into' stored procedure not work? - sql

Question

I'm running Oracle SQL developer and I've got the following Stored Procedure. I'm quite new to this but really not sure why this isn't working:
CREATE OR REPLACE PROCEDURE CHECKDUPLICATE(
username1 IN USERS.USERNAME%TYPE,
o_username OUT USERS.USERNAME%TYPE
)
IS
BEGIN
SELECT USERNAME
INTO o_username
FROM USERS WHERE username1 = o_username;
END;
When I try to call it:
DECLARE
o_username USERS.USERNAME%TYPE;
BEGIN
CHECKDUPLICATE('Jacklin', o_username);
DBMS_OUTPUT.PUT_LINE('username : ' || o_username);
END;
I get the error message:
Error starting at line 1 in command:
DECLARE
o_username USERS.USERNAME%TYPE;
BEGIN
CHECKDUPLICATE(Jacklin, o_username);
DBMS_OUTPUT.PUT_LINE('username : ' || o_username);
END;
Error report:
ORA-06550: line 5, column 19:
PLS-00201: identifier 'JACKLIN' must be declared
ORA-06550: line 5, column 4:
PL/SQL: Statement ignored
06550. 00000 - "line %s, column %s:\n%s"
*Cause: Usually a PL/SQL compilation error.
*Action:
What does it mean by "Identifier 'Jacklin' must be declared? (Table is called USERS, and column name is called USERNAME). Any help would be appreciated.
EDIT** I put Jacklin in quotes, and I get this message now:
Error report:
ORA-01403: no data found
ORA-06512: at "L13JAV04.CHECKDUPLICATE", line 9
ORA-06512: at line 6
01403. 00000 - "no data found"
*Cause:
*Action:
Even though Jacklin does it exist in the database!

Answer 1

Once you quote 'Jacklin' so that it's treated as a string literal rather than an identifier, your SQL statement doesn't look right.
SELECT USERNAME
INTO o_username
FROM USERS
WHERE username1 = o_username;
My wager is that you want to use the input parameter in your WHERE clause, not the output parameter.
SELECT USERNAME
INTO o_username
FROM USERS
WHERE username1 = username;
It doesn't make sense to check the value of an output parameter when you haven't done anything to initialize it.
But your code still doesn't seem to make sense. A SELECT INTO will throw an error if anything other than 1 row is returned. If your query returns 0 rows, you'll get a NO_DATA_FOUND exception. If your query returns more than 1 row, you'll get a TOO_MANY_ROWS exception. Your procedure is named CheckDuplicate so I'm guessing that it's purpose is to check whether a particular username already exists in the table rather than trying to insert it and catching the unique constraint violation error. If that is the intention of your code
You probably want it to be a function
You probably don't want to return the username
You probably want to return an indicator of whether the username already exists
My guess, therefore, is that you would want something like
create or replace function isAvailable( p_username IN USERS.USERNAME%TYPE )
return Boolean
is
l_username USERS.USERNAME%TYPE;
begin
select username
into l_username
from users
where username = p_username;
return false;
exception
when no_data_found
then
return true;
end;

Answer 2

You need to put Jacklin within quotes for it to be treateed as a string. Otherwise the parser thinks it's a field name.

Answer 3

There would have been no user by name of "Jacklin" thats why its giving you the error. Please add an exception at the end
WHEN NO_DATA_FOUND
THEN
......