SQL Query alter table auto increment in SQL Plus Oracle 10g - oracle

Question

I have this SQL Query and I am trying to modify my column so it has an auto increment Property, But when I execute the query I either have a problem code ORA-00933 SQL command not properly ended
This is what I have tried
ALTER TABLE BF_USER DROP COLUMN USER_ID
ALTER TABLE BF_USER ADD USER_ID INT IDENTITY(1,1);

Answer 1

SQL*Plus is Oracle's command-line tool. In that case:
SQL> create table bf_user (user_id number, name varchar2(10));
Table created.
SQL> alter table bf_user drop column user_id;
Table altered.
SQL> alter table bf_user add user_id number generated always as identity;
Table altered.
Testing:
SQL> insert into bf_user(name) values ('Littlefoot');
1 row created.
SQL> select * from bf_user;
NAME USER_ID
---------- ----------
Littlefoot 1
SQL>
As you use Oracle 10g (which doesn't support identity columns), use combination of a sequence and a database trigger:
SQL> create table bf_user (user_id number, name varchar2(10));
Table created.
SQL> create sequence bf_seq;
Sequence created.
SQL> create or replace trigger trg_bi_bfu
2 before insert on bf_user
3 for each row
4 begin
5 select bf_seq.nextval into :new.user_id from dual;
6 end;
7 /
Trigger created.
SQL> insert into bf_user (name) values ('Nayeon');
1 row created.
SQL> select * from bf_user;
USER_ID NAME
---------- ----------
1 Nayeon
SQL>