考虑表 COMPANY 有以下记录

www.yiibai.com

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 | yiibai.com |  24 | Houston2   |  10000
(7 rows)
 yiibai.com 

下面是简单的例子，显示PostgreSQL的逻辑运算符的用法。年龄大于或等于25并且工资大于或等于65000.00了所有的记录，下面的SELECT语句列表：

www.yiibai.com

testdb=# SELECT * FROM COMPANY WHERE AGE >= 25 AND SALARY >= 6500; www.yiibai.com 

以上PostgreSQL表会产生以下结果： www.yiibai.com

 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)
 
yiibai.com
 

年龄大于或等于25或薪水大于或等于65000.00所有的记录列表，下面的SELECT语句： yiibai.com

testdb=# SELECT * FROM COMPANY WHERE AGE >= 25 OR SALARY >= 6500; www.yiibai.com 

以上PostgreSQL的表会产生以下结果： yiibai.com

 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)
 yiibai.com 

下面的SELECT语句列表年龄不为NULL，这意味着所有记录下来，因为记录是没有年龄等于NULL： www.yiibai.com

testdb=#  SELECT * FROM COMPANY WHERE SALARY IS NOT NULL; www.yiibai.com 

以上PostgreSQL的表会产生以下结果：

 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) 
yiibai.com