If condition is giving Error in Oracle Package - oracle

Question

I'm new to oracle database i created a PL/SQL package with some if else statements. It contains three procedures respectively for insert, update and delete. That is giving me error. Can anyone help me sorting out this..
create or replace
PACKAGE body USERS_tapi
IS
-- insert
PROCEDURE ins(
p_FIRSTNAME IN USERS.FIRSTNAME%type ,
p_ADDRESS IN USERS.ADDRESS%type ,
p_ROLEID IN USERS.ROLEID%type DEFAULT NULL ,
p_USERNAME IN USERS.USERNAME%type ,
p_PASSWORD IN USERS.PASSWORD%type ,
p_USERID IN USERS.USERID%type ,
p_LASTNAME IN USERS.LASTNAME%type,
O_val OUT NUMBER
)
IS
BEGIN
select count(*) as cnt from USERS where username=p_USERNAME and password=p_PASSWORD;
if cnt = 0 then
INSERT INTO USERS(
FIRSTNAME ,
ADDRESS ,
ROLEID ,
USERNAME ,
PASSWORD ,
USERID ,
LASTNAME
)
VALUES
(
p_FIRSTNAME ,
p_ADDRESS ,
p_ROLEID ,
p_USERNAME ,
p_PASSWORD ,
USERS_SEQ.nextval ,
p_LASTNAME
);
O_val:=0;
else if cnt > 0 then
O_val:=1;
else
O_val:=2;
END IF;
return O_val;
END;
-- update
PROCEDURE upd
(
p_FIRSTNAME IN USERS.FIRSTNAME%type ,
p_ADDRESS IN USERS.ADDRESS%type ,
p_ROLEID IN USERS.ROLEID%type DEFAULT NULL ,
p_USERNAME IN USERS.USERNAME%type ,
p_PASSWORD IN USERS.PASSWORD%type ,
p_USERID IN USERS.USERID%type ,
p_LASTNAME IN USERS.LASTNAME%type
)
IS
BEGIN
UPDATE USERS
SET FIRSTNAME = p_FIRSTNAME ,
ADDRESS = p_ADDRESS ,
ROLEID = p_ROLEID ,
USERNAME = p_USERNAME ,
PASSWORD = p_PASSWORD ,
LASTNAME = p_LASTNAME
WHERE USERID = p_USERID;
END;
-- del
PROCEDURE del(
p_USERID IN USERS.USERID%type )
IS
BEGIN
DELETE FROM USERS WHERE USERID = p_USERID;
END;
END USERS_tapi;

Answer 1

Use elsif instead of else if in the following line :
else if cnt > 0 then
The former is just one more case in your condition block.
The latter syntax is starting a nested condition block in the else part of the first condition block. That nested block would need its own END IF to work.
You could also use a CASE statement :
CASE
WHEN cnt = 0 then
-- insert statement
O_val:=0;
WHEN cnt > 0 then
O_val:=1;
else
O_val:=2;
END CASE;