Print a rollback query of a update query using a query - oracle

Question

I need to print the rollback query of a update query.
My original query is
UPDATE EMPLOYEE SET NAME = 'SAMAN' WHERE ID=4;
The corresponding update for above query is
UPDATE EMPLOYEE SET NAME=(SELECT NAME FROM EMPLOYEE WHERE ID=4);
I need to print a query to rollback if above original query went wrong. I need it to print it via using a query also.
I'm using oracle 11g database.

Answer 1

You can do it by running a select query like below,
SELECT 'UPDATE EMPLOYEE SET NAME = '''||name||''' WHERE id = '||id||';' FROM employee;
and of course, run the select query before your update query.

Answer 2

As far as I understood the question, it is some kind of a log table you're looking for. I have no idea what you mean by "printing the rollback query"; never heard of anything like that.
So, let me demonstrate what I have on my mind. Review it, apply if it makes sense in your case. The code is commented, I hope you'll understand it
Prepare the scene:
SQL> -- Log table
SQL> create table emp_log
2 (id number constraint pk_el primary key,
3 empno number constraint fk_el_emp references emp (empno) not null,
4 datum date not null,
5 ename varchar2(20)
6 );
Table created.
SQL> -- A sequence which will be used to populate the ID column in the EMP_LOG table
SQL> create sequence seqa;
Sequence created.
SQL> -- Trigger; if new ENAME is different from the last one, log the change (i.e.
SQL> -- store the old ENAME)
SQL> create or replace trigger trg_bu_emp
2 before update on emp
3 for each row
4 begin
5 if :new.ename <> :old.ename then
6 insert into emp_log (id, empno, datum, ename)
7 values (seqa.nextval, :new.empno, sysdate, :old.ename);
8 end if;
9 end;
10 /
Trigger created.
OK, let's see how it works:
SQL> -- Some employees in department 10
SQL> select empno, ename from emp where deptno = 10;
EMPNO ENAME
---------- ----------
7782 CLARK
7839 KING
7934 MILLER
SQL> -- Update KING's name to a better one (just kidding)
SQL> update emp set ename = 'LITTLEFOOT' where empno = 7839;
1 row updated.
SQL> -- What's in the log?
SQL> select * From emp_log order by id desc;
ID EMPNO DATUM ENAME
---------- ---------- ------------------- --------------------
5 7839 30.03.2018 20:22:15 KING
SQL> -- I don't like the new name after all; return the previous one
SQL> update emp e set
2 e.ename = (select l.ename from emp_log l
3 where l.empno = e.empno
4 and l.id = (select max(l1.id) from emp_log l1
5 where l1.empno = l.empno
6 )
7 )
8 where e.empno = 7839;
1 row updated.
SQL> -- What we've done?
SQL> select empno, ename from emp where deptno = 10;
EMPNO ENAME
---------- ----------
7782 CLARK
7839 KING
7934 MILLER
SQL> -- What's in the log now?
SQL> select * From emp_log order by id desc;
ID EMPNO DATUM ENAME
---------- ---------- ------------------- --------------------
6 7839 30.03.2018 20:22:33 LITTLEFOOT
5 7839 30.03.2018 20:22:15 KING
SQL>