Add a primary key column to a table

SQL> drop table T1 purge;

The table has been deleted.

SQL> Create Table T1 as select * from EMP;

The table has been created.

SQL> ALTER TABLE T1 Add a varchar2 (20 );

The table has been changed.

SQL> select * from T1;

Empno ename job Mgr hiredate Sal comm deptno
-------------------------------------------------------------------------------------------------------
7369 Smith clerk 7902-12-80 800 20
7499 Allen salesman 7698 20-2 month-81 1600 300 30
7521 ward salesman 7698 22-2 month-81 1250 500 30
7566 Jones manager 7839 2975-81 20
7654 Martin salesman 7698 28-9 month-81 1250 1400 30
7698 Blake manager 7839 01-5 months-81 2850 30
7782 Clark manager 7839-81 2450 10
7839 King President 17-11 month-81 5000 10
7844 Turner salesman 7698 month-81 1500 0 30
7900 James Clerk 7698 03-12 months-81 950 30
7902 Ford analyst 7566 03-12 months-81 3000 20

Empno ename job Mgr hiredate Sal comm deptno
-------------------------------------------------------------------------------------------------------
7934 Miller clerk 7782 23-1 month-82 1300 10

12 rows have been selected.

SQL> Update T1 set a = ('zjs' | '000000' | to_char (rownum, 'fm000000000 '));

12 rows have been updated.

SQL> select * from T1;

Empno ename job Mgr hiredate Sal comm deptno
-------------------------------------------------------------------------------------------------------
7369 Smith clerk 7902-12 month-80 800 20 zjs2012010000000001
7499 Allen salesman 7698 20-2 month-81 1600 300 30 zjs2012010000000002
7521 ward salesman 7698 22-2 month-81 1250 500 30 zjs2012010000000003
7566 Jones manager 7839 2975-81 20 zjs2012010000000004
7654 Martin salesman 7698 28-9 month-81 1250 1400 30 zjs2012010000000005
7698 Blake manager 7839 01-5 month-81 2850 30 zjs2012010000000006
7782 Clark manager 7839 09-6 month-81 2450 10 zjs2012010000000007
7839 King President 17-11 month-81 5000 10 zjs201201020.00008
7844 Turner salesman 7698 month-81 1500 0 30 zjs201201020.00009
7900 James Clerk 7698 03-12 month-81 950 30 zjs2012010000000010
7902 Ford analyst 7566 03-12 month-81 3000 20 zjs2012010000000011

Empno ename job Mgr hiredate Sal comm deptno
-------------------------------------------------------------------------------------------------------
7934 Miller clerk 7782 23-1 month-82 1300 10 zjs2012010000000012

12 rows have been selected.