SQL*Plus: Release 10.2.0.1.0 - Production on Sat Sep 25 06:40:40 2010

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SQL> connect
Enter user-name: system
Enter password:
Connected.
SQL> select * from emp;

ID NAME SAL JOB HIREDATE DEPTNO
---------- --------------- ---------- ---------- --------- ----------
ADDS
---------------
100 Johan 1300 CLERK 21-SEP-10 10
HYD


SQL> desc emp;
Name Null? Type
----------------------------------------- -------- ----------------------------

ID NOT NULL NUMBER(6)
NAME VARCHAR2(15)
SAL NOT NULL NUMBER(10)
JOB VARCHAR2(10)
HIREDATE DATE
DEPTNO NUMBER(5)
ADDS VARCHAR2(15)

SQL> create table kota as select * from emp;

Table created.

SQL> select * from kota;

ID NAME SAL JOB HIREDATE DEPTNO
---------- --------------- ---------- ---------- --------- ----------
ADDS
---------------
100 Johan 1300 CLERK 21-SEP-10 10
HYD


SQL> desc kota;
Name Null? Type
----------------------------------------- -------- ----------------------------

ID NUMBER(6)
NAME VARCHAR2(15)
SAL NOT NULL NUMBER(10)
JOB VARCHAR2(10)
HIREDATE DATE
DEPTNO NUMBER(5)
ADDS VARCHAR2(15)

Question emp table is the base table ,when was going for copy the table(kota) base table to kota "all constraints('primary key') not coming why ? i try to modify those tables but no use.please let me share my problem .

If I understand correctly you ask why the is no primary key on "kota"? Because you didn't define any... You told oracle to "create table kota as select * from emp". That's it. You have to use some ALTER TABLE after that step and define a primary key.