Oracle Database Discussions

Hi ,
We are on 11.2.0.2 on Solaris 10. I have a need to convert a column which is a number data type to a VARCHAR2 data type. The table has data and the column is part of the primary key. Is it possible? How best can one go about it?

 
SQL>  create table test1 
(object_name varchar2(30) NOT NULL, object_id number NOT NULL); 


Table created. 

SQL>ALTER TABLE TEST1 add(constraint test1_pk primary key (OBJECT_NAME,OBJECT_ID)); 


Table altered. 

SQL> INSERT INTO TEST1 VALUES('EMP',1); 

1 row created. 

SQL> ED 
Wrote file afiedt.buf 

  1* INSERT INTO TEST1 VALUES('DEPT',2) 
SQL> / 

1 row created. 

SQL> COMMIT; 

Commit complete. 

SQL> ALTER TABLE TEST1 MODIFY (OBJECT_ID VARCHAR2(20)); 
ALTER TABLE TEST1 MODIFY (OBJECT_ID VARCHAR2(20)) 
                          * 
ERROR at line 1: 
ORA-01439: column to be modified must be empty to change datatype