Finding duplicate names

Question

I want to find duplicate names from my database I wrote the following query. But it is displaying more that existing records. I guess it is taking cartesian product.
select a.name from emp from emp a,emp b where a.name=b.name;
can anyone correct this query.
I want to display all the duplicate records having same names...
for example for the following table. I want to display result having same dname like
DEPTNO DNAME LOC
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
50 SALES hyd
output should be
30 sales chicago
50 sales hyd

Answer 1

Welcome to OTN.
From your initial sample data - i didn't find anything duplicate. They all are unique if you consider deptno.
But, i assume you have plenty of redundant data. So, your query may be look like ->
satyaki>
satyaki>select * from v$version;
BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Prod
PL/SQL Release 10.2.0.3.0 - Production
CORE    10.2.0.3.0      Production
TNS for 32-bit Windows: Version 10.2.0.3.0 - Production
NLSRTL Version 10.2.0.3.0 - Production
Elapsed: 00:00:00.16
satyaki>
satyaki>
satyaki>create table dup_emp
  2     as
  3       select k.*
  4       from (
  5              select * from emp
  6              union all
  7              select * from emp
  8              where rownum < 6
  9            ) k;
Table created.
Elapsed: 00:00:03.90
satyaki>
satyaki>
satyaki>select * from dup_emp;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
      9999 SATYAKI    SLS             7698 02-NOV-08      55000       3455         10
      7777 SOURAV     SLS                  14-SEP-08      45000       3400         10
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       4450                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       7000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      9999 SATYAKI    SLS             7698 02-NOV-08      55000       3455         10
      7777 SOURAV     SLS                  14-SEP-08      45000       3400         10
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
18 rows selected.
Elapsed: 00:00:00.32
satyaki>
satyaki>
satyaki>select empno, count(empno)
  2  from dup_emp
  3  group by empno
  4  having count(empno) > 1;
     EMPNO COUNT(EMPNO)
      9999            2
      7777            2
      7521            2
      7566            2
      7654            2
Elapsed: 00:00:00.11
satyaki>
satyaki>
satyaki>Regards.
Satyaki De.