Using "BEGIN" keyword improperly - sql

Question

I am getting an error in the code below. I have added an arror <------ where the problem is.
The error message says that a THEN is expected, but when I use THEN, then it says that a BEGIN is expected.
Error(27,6): PLS-00103: Encountered the symbol "BEGIN" when expecting one of the following: then and or The symbol "then" was substituted for "BEGIN" to continue.
Error(30,6): PLS-00103: Encountered the symbol "END" when expecting one of the following: , ; return returning
What am I doing wrong?
create or replace PROCEDURE "sp_updateUserPassword"(newUserPwd IN VARCHAR2, curIsoUserUID IN NUMBER)
IS
curUserID NUMBER;
userDateCreated DATE;
oldUserPwd VARCHAR2(255);
BEGIN
SELECT ISOUID INTO curUserID FROM ISOUSERS WHERE ISOUID=curIsoUserUID;
SELECT DATECREATE INTO userDateCreated FROM ISOUSERS WHERE ISOUID=curIsoUserUID;
SELECT PASSWORD INTO oldUserPwd FROM ISOUSERS WHERE ISOUID=curIsoUserUID;
IF(newUserPwd = oldUserPwd)
THEN
raise_application_error(-20000, 'The new password must be different from the previous password');
RETURN;
END IF;
IF NOT EXISTS
(
SELECT ISOUID
FROM OLDUSERPASSWORDS
WHERE ISOUID=curIsoUserUID
)
BEGIN <------------ Error is here
INSERT INTO OLDUSERPASSWORDS(ISOUID, DATECREATE, DATELASTCHANGE, CURRENTPASS, OLDPASS)
VALUES(curUserID, userDateCreated, SYSDATE, newUserPwd, oldUserPwd)
END;
/*raise_application_error(-20000, 'TEST');*/
END "sp_updateUserPassword";
Update
Corrected the code, so it now looks like this:
IF NOT EXISTS
(
SELECT ISOUID
FROM OLDUSERPASSWORDS
WHERE ISOUID=curIsoUserUID
)
THEN
BEGIN
INSERT INTO OLDUSERPASSWORDS(ISOUID, DATECREATE, DATELASTCHANGE, CURRENTPASS, OLDPASS)
VALUES(curUserID, userDateCreated, SYSDATE, newUserPwd, oldUserPwd)
END;
END IF;
I am getting this error:
Error(30,7): PL/SQL: ORA-00933: SQL command not properly ended
Error(31,7): PLS-00103: Encountered the symbol "IF" when expecting one of the following: ; <an identifier> <a double-quoted delimited-identifier>
Perhaps it's just a minor error that I am missing?

Answer 1

PL/SQL Syntax Error for IF THEN ELSE
Correct syntax is:
IF condition THEN
statements
END IF;
Your code is effectively:
IF condition THEN
BEGIN
statements
END;
Corrected
IF NOT EXISTS
(
SELECT ISOUID
FROM OLDUSERPASSWORDS
WHERE ISOUID=curIsoUserUID
)
THEN
BEGIN <------------ Error is NOT here
INSERT INTO OLDUSERPASSWORDS(ISOUID, DATECREATE, DATELASTCHANGE, CURRENTPASS, OLDPASS)
VALUES(curUserID, userDateCreated, SYSDATE, newUserPwd, oldUserPwd);
END;
END IF;

Answer 2

You are getting your first error because you need to add a THEN clause before the BEGIN block to make the syntax of the ID statement complete and correct.
You are getting the second error:
Error(30,7): PL/SQL: ORA-00933: SQL command not properly ended
because you have not completed your INSERT statement. Terminate it with a semicolon and that should fix that error.
IF NOT EXISTS
(
SELECT ISOUID
FROM OLDUSERPASSWORDS
WHERE ISOUID=curIsoUserUID
)
THEN
BEGIN
INSERT INTO OLDUSERPASSWORDS(ISOUID, DATECREATE, DATELASTCHANGE, CURRENTPASS, OLDPASS)
VALUES(curUserID, userDateCreated, SYSDATE, newUserPwd, oldUserPwd);
END;
END IF;

Answer 3

You forgot the THEN before the BEGIN, that goes with the IF NOT EXISTS.