PostgreSQL UNION

PostgreSQL UNION clause/operator is used to combine the results of two or more SELECT statements without returning any duplicate rows

postgres=# select * from tab1;   postgres=# select * from tab2;
 id | name                              id |  name  
----+-------                           ----+--------
  1 | nijam                              1 | jamal
  2 | abu                                2 | smith
  3 | umar                               4 | daniel
  7 | jamal                              5 | zaheer
(4 rows)                               (4 rows)

postgres=# select name from tab1 union select name from tab2;    
  name  
--------
 smith
 daniel
 zaheer
 nijam
 abu
 jamal
 umar
(7 rows)