Working with Duplicate Rows in SQL

Duplicate Rows :

• The default display of queries is all rows, including duplicate rows
• postgres=# select deptno from emp;
  deptno
  --------
  20
  30
  30
  20
  30
  30
  10
  20
  10
  30
  20
  30
  20
  10
  (14 rows)

Selecting Unique Rows (Deleting Duplicates) :

• postgres=# select distinct deptno from emp;

deptno
--------
10
20
30
(3 rows)