Distinct Rows

The keyword DISTINCT prevents duplicates from being returned: SELECT DISTINCT .... FROM table WHERE condition

Example:

workshop=# SELECT * FROM stud; id | name | semester | diploma | gender ----+------+----------+---------+----- 1 | fred | 2 | bio | m 3 | tom | 1 | bio | m 4 | john | 3 | phy | m 2 | lisa | 2 | bio | f (4 rows) workshop=# SELECT DISTINCT gender FROM stud; gender ----- f m (2 rows) Note that DISTINCT operates on all the columns selected in the query together, thus a difference in one of them is enough to be distinct: workshop=# SELECT DISTINCT gender, diploma FROM stud; gender | diploma --------+--------- f | bio m | bio m | phy (3 rows)