Postgresql 简明教程

AND and OR Conjunctive Operators

PostgreSQL AND 和 OR 运算符用于组合多个条件，以缩小 PostgreSQL 语句中选择的数据范围。这两个运算符称为结合运算符。

The PostgreSQL AND and OR operators are used to combine multiple conditions to narrow down selected data in a PostgreSQL statement. These two operators are called conjunctive operators.

这些运算符提供了一种在同一 PostgreSQL 语句中使用不同运算符进行多个比较的方法。

These operators provide a means to make multiple comparisons with different operators in the same PostgreSQL statement.

The AND Operator

AND 运算符允许在 PostgreSQL 语句的 WHERE 子句中存在多个条件。在使用 AND 运算符时，当所有条件都为 true 时，将假定完整条件为 true。例如，仅当 condition1 和 condition2 都为 true 时，[condition1] AND [condition2] 才为 true。

The AND operator allows the existence of multiple conditions in a PostgreSQL statement’s WHERE clause. While using AND operator, complete condition will be assumed true when all the conditions are true. For example [condition1] AND [condition2] will be true only when both condition1 and condition2 are true.

Syntax

AND 运算符与 WHERE 子句的基本语法如下 −

The basic syntax of AND operator with WHERE clause is as follows −

SELECT column1, column2, columnN
FROM table_name
WHERE [condition1] AND [condition2]...AND [conditionN];

您可以使用 AND 运算符组合 N 个条件。PostgreSQL 语句执行某个操作（无论是事务还是查询），AND 分隔的所有条件都必须为 TRUE。

You can combine N number of conditions using AND operator. For an action to be taken by the PostgreSQL statement, whether it be a transaction or query, all conditions separated by the AND must be TRUE.

Example

考虑 COMPANY 表具有以下记录：

Consider the table COMPANY having records as follows −

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 SELECT 语句列出了所有 AGE 大于或等于 25 AND 且 salary 大于或等于 65000.00 的记录 −

The following SELECT statement lists down all the records where AGE is greater than or equal to 25 AND salary is greater than or equal to 65000.00 −

testdb=# SELECT * FROM COMPANY WHERE AGE >= 25 AND SALARY >= 65000;

以上给出的 PostgreSQL 语句将产生以下结果 -

The above given PostgreSQL statement will produce the following result −

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

The OR Operator

OR 运算符也用于组合 PostgreSQL 语句的 WHERE 子句中的多个条件。在使用 OR 运算符时，当至少任何一个条件为 true 时，将假定完整条件为 true。例如，如果 condition1 或 condition2 是 true，则 [condition1] OR [condition2] 将为 true。

The OR operator is also used to combine multiple conditions in a PostgreSQL statement’s WHERE clause. While using OR operator, complete condition will be assumed true when at least any of the conditions is true. For example [condition1] OR [condition2] will be true if either condition1 or condition2 is true.

Syntax

OR 运算符与 WHERE 子句的基本语法如下 −

The basic syntax of OR operator with WHERE clause is as follows −

SELECT column1, column2, columnN
FROM table_name
WHERE [condition1] OR [condition2]...OR [conditionN]

您可以使用 OR 运算符组合 N 个条件。PostgreSQL 语句执行某个操作（无论是事务还是查询），OR 分隔的条件中只需任何一个为 TRUE。

You can combine N number of conditions using OR operator. For an action to be taken by the PostgreSQL statement, whether it be a transaction or query, only any ONE of the conditions separated by the OR must be TRUE.

Example

考虑 COMPANY 表，其中包含以下记录 −

Consider the COMPANY table, having the following records −

 # 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 SELECT 语句列出所有 AGE 大于或等于 25 OR 薪水大于或等于 65000.00 的记录 -

The following SELECT statement lists down all the records where AGE is greater than or equal to 25 OR salary is greater than or equal to 65000.00 −

testdb=# SELECT * FROM COMPANY WHERE AGE >= 25 OR SALARY >= 65000;

以上给出的 PostgreSQL 语句将产生以下结果 -

The above given PostgreSQL statement will produce the following result −

 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)