DROP TABLE FOLLOWERS_LIST PURGE

create table FOLLOWERS_LIST (USER_NAME VARCHAR2 (20 CHAR), F_USER_NAME VARCHAR2 (20 CHAR))

DROP TABLE FINAL_TABLE PURGE

create table FINAL_TABLE (USER_NAME VARCHAR2 (20 CHAR), M_USER VARCHAR2 (20 CHAR), TOTAL NUMBER, FOLLOWER NUMBER DEFAULT NULL)

INSERT ALL 
INTO FOLLOWERS_LIST VALUES ('user 1', 'user2') 
INTO FOLLOWERS_LIST VALUES ('user 1', 'user3') 
INTO FOLLOWERS_LIST VALUES ('user 3', 'user4') 
select 1 from dual

commit

INSERT ALL 
INTO FINAL_TABLE VALUES ('user 1', 'user2',8,null) 
INTO FINAL_TABLE VALUES ('user 2', 'user3',9,null) 
INTO FINAL_TABLE VALUES ('user 3', 'user4',2,null) 
select 1 from dual

commit

UPDATE Final_table FB 
  SET FB.FOLLOWER = 
        (SELECT CASE WHEN COUNT(*) > 0 THEN 1 
                           ELSE  0 END 
            FROM FOLLOWERS_LIST fl 
            WHERE FB.USER_NAME = FL.USER_NAME AND FB.M_USER = FL.F_USER_NAME)

            commit

SELECT * FROM Final_table