PostgreSQL 比较运算符

考虑下面的表公司其记录如下−

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 | James |  24 | Houston   |  10000
(7 rows)

以下是使用PostgresSQL比较操作符的简单示例。

在这里，我们使用了 WHERE 子句，该子句将在单独的章节中解释，但目前您可以理解WHERE子句用于在SELECT语句中加入条件语句。

以下SELECT语句列出了所有工资大于50,000.00的记录 –

testdb=# SELECT * FROM COMPANY WHERE SALARY > 50000;

以上提供的PostgreSQL语句将生成以下结果 –

id | name  | age |address    | salary
----+-------+-----+-----------+--------
  4 | Mark  |  25 | Rich-Mond |  65000
  5 | David |  27 | Texas     |  85000
(2 rows)

下面的SELECT语句列出了所有工资为20,000.00的记录−

testdb=#  SELECT * FROM COMPANY WHERE SALARY = 20000;

给定的PostgreSQL语句将产生以下结果−

id | name  | age |  address    | salary
 ----+-------+-----+-------------+--------
   1 | Paul  |  32 | California  |  20000
   3 | Teddy |  23 | Norway      |  20000
(2 rows)

下面的SELECT语句列出了所有工资不等于20,000.00的记录 −

testdb=#  SELECT * FROM COMPANY WHERE SALARY != 20000;

给定的PostgreSQL语句将产生如下结果−

id | name  | age |  address    | salary
----+-------+-----+-------------+--------
  2 | Allen |  25 | Texas       |  15000
  4 | Mark  |  25 | Rich-Mond   |  65000
  5 | David |  27 | Texas       |  85000
  6 | Kim   |  22 | South-Hall  |  45000
  7 | James |  24 | Houston     |  10000
(5 rows)

以下SELECT语句列出所有薪资不等于20,000.00的记录−

testdb=# SELECT * FROM COMPANY WHERE SALARY <> 20000;

给定的PostgreSQL语句将产生以下结果 –

id | name  | age | address    | salary
----+-------+-----+------------+--------
  2 | Allen |  25 | Texas      |  15000
  4 | Mark  |  25 | Rich-Mond  |  65000
  5 | David |  27 | Texas      |  85000
  6 | Kim   |  22 | South-Hall |  45000
  7 | James |  24 | Houston    |  10000
(5 rows)

下面的SELECT语句列出了所有薪水大于或等于65,000.00的记录−

testdb=# SELECT * FROM COMPANY WHERE SALARY >= 65000;

上述给出的PostgreSQL语句将产生以下结果−

id | name  | age |  address  | salary
----+-------+-----+-----------+--------
  4 | Mark  |  25 | Rich-Mond |  65000
  5 | David |  27 | Texas     |  85000
(2 rows)