考虑表 COMPANY 有以下记录
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)
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:
testdb=# SELECT * FROM COMPANY WHERE AGE >= 25 AND SALARY >= 6500;
以上PostgreSQL表会产生以下结果:
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:
testdb=# SELECT * FROM COMPANY WHERE AGE >= 25 OR SALARY >= 6500;
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)
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:
testdb=# SELECT * FROM COMPANY WHERE SALARY IS NOT NULL;
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)