考慮表 COMPANY 有以下記錄

testdb# select * from COMPANY;
 id | name  | age | address   | salary
----+-------+-----+-----------+--------
  1 | Paul  |  32 | California|  20000
  2 | Allen |  25 | Texas     |  15000
  3 | Teddy |  23 | Norway    |  20000
  4 | Mark  |  25 | Rich-Mond |  65000
  5 | David |  27 | Texas     |  85000
  6 | Kim   |  22 | South-Hall|  45000
  7 | gitbook.net |  24 | Houston2   |  10000
(7 rows)

下麵是簡單的例子，顯示PostgreSQL的邏輯運算符的用法。年齡大於或等於25並且工資大於或等於65000.00了所有的記錄，下麵的SELECT語句列表：

testdb=# SELECT * FROM COMPANY WHERE AGE >= 25 AND SALARY >= 6500;

以上PostgreSQL表會產生以下結果：

 id | name  | age |                      address                  | salary
----+-------+-----+-----------------------------------------------+--------
  1 | Paul  |  32 | California                                    |  20000
  2 | Allen |  25 | Texas                                         |  15000
  4 | Mark  |  25 | Rich-Mond                                     |  65000
  5 | David |  27 | Texas                                         |  85000
(4 rows)

年齡大於或等於25或薪水大於或等於65000.00所有的記錄列表，下麵的SELECT語句：

testdb=# SELECT * FROM COMPANY WHERE AGE >= 25 OR SALARY >= 6500;

以上PostgreSQL的表會產生以下結果：

 id | name  | age |  address    | salary
----+-------+-----+-------------+--------
  1 | Paul  |  32 | California  |  20000
  2 | Allen |  25 | Texas       |  15000
  3 | Teddy |  23 | Norway      |  20000
  4 | Mark  |  25 | Rich-Mond   |  65000
  5 | David |  27 | Texas       |  85000
  6 | Kim   |  22 | South-Hall  |  45000
  7 | James |  24 | Houston     |  10000
  8 | Paul  |  24 | Houston     |  20000
  9 | James |  44 | Norway      |   5000
 10 | James |  45 | Texas       |   5000
(10 rows)

下麵的SELECT語句列表年齡不為NULL，這意味著所有記錄下來，因為記錄是冇有年齡等於NULL：

testdb=#  SELECT * FROM COMPANY WHERE SALARY IS NOT NULL;

以上PostgreSQL的表會產生以下結果：

 id | name  | age |  address    | salary
----+-------+-----+-------------+--------
  1 | Paul  |  32 | California  |  20000
  2 | Allen |  25 | Texas       |  15000
  3 | Teddy |  23 | Norway      |  20000
  4 | Mark  |  25 | Rich-Mond   |  65000
  5 | David |  27 | Texas       |  85000
  6 | Kim   |  22 | South-Hall  |  45000
  7 | James |  24 | Houston     |  10000
  8 | Paul  |  24 | Houston     |  20000
  9 | James |  44 | Norway      |   5000
 10 | James |  45 | Texas       |   5000
(10 rows)