Primary key for an column consisting duplicates

Question

hi,
------->i have created a table and
-------> i have a column consisting of 1000 records (but where i have duplicates)
and now i want to create a primary key for the column
how can i do it....

Answer 1

Hi,
You can find records which contains duplicate values for the table column using Oracle exceptions table. Please see a small demonstration:-
SQL> create table test1(id number);
Table created.
SQL> insert into test1 values(&id);
Enter value for id: 1
old 1: insert into test1 values(&id)
new 1: insert into test1 values(1)
1 row created.
SQL> /
Enter value for id: 2
old 1: insert into test1 values(&id)
new 1: insert into test1 values(2)
1 row created.
SQL> /
Enter value for id: 3
old 1: insert into test1 values(&id)
new 1: insert into test1 values(3)
1 row created.
SQL> /
Enter value for id: 1
old 1: insert into test1 values(&id)
new 1: insert into test1 values(1)
1 row created.
SQL> /
Enter value for id: 3
old 1: insert into test1 values(&id)
new 1: insert into test1 values(3)
1 row created.
SQL> /
Enter value for id: 4
old 1: insert into test1 values(&id)
new 1: insert into test1 values(4)
1 row created.
SQL> /
Enter value for id: 5
old 1: insert into test1 values(&id)
new 1: insert into test1 values(5)
1 row created.
SQL> commit;
Commit complete.
SQL> alter table test1 add constraint id_pk primary key(id);
alter table test1 add constraint id_pk primary key(id)
ERROR at line 1:
ORA-02437: cannot validate (SYS.ID_PK) - primary key violated
SQL> alter table test1 add constraint id_pk primary key(id) exceptions into exceptions;
alter table test1 add constraint id_pk primary key(id) exceptions into exceptions
ERROR at line 1:
ORA-02445: Exceptions table not found
SQL> @?/rdbms/admin/utlexcpt
Table created.
SQL> alter table test1 add constraint id_pk primary key(id) exceptions into exceptions;
alter table test1 add constraint id_pk primary key(id) exceptions into exceptions
ERROR at line 1:
ORA-02437: cannot validate (SYS.ID_PK) - primary key violated
SQL> desc exceptions
Name Null? Type
ROW_ID ROWID
OWNER VARCHAR2(30)
TABLE_NAME VARCHAR2(30)
CONSTRAINT VARCHAR2(30)
SQL> select * from exceptions;
ROW_ID OWNER TABLE_NAME CONSTRAINT
AAAc95AABAAA9EpAAD SYS TEST1 ID_PK
AAAc95AABAAA9EpAAA SYS TEST1 ID_PK
AAAc95AABAAA9EpAAE SYS TEST1 ID_PK
AAAc95AABAAA9EpAAC SYS TEST1 ID_PK
SQL> select * from test1 where rowid in(select row_id from exceptions);
ID
3
1
1
3
Thanks
Edited by: rarain on May 28, 2013 12:10 PM