最近几年来，地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持，如城市管理、区划、环境整治等等，地理信息成为信息时代重要的组成部分之一； “数字地球”概念的提出，更进一步推动了作为其技术支撑的GIS的发展。 与此同时，一些学者致力于相关的理论研究，如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面，并且这两个方面构成了相互促进的发展过程。
In PostgreSQL, AND and OR, also known as join operators, are used to narrow the scope of a query when querying data, and we can specify one or more query conditions with AND or OR. The AND operator indicates that one or more conditions must be true at the same time. In Create the COMPANY table ( 下载 COMPANY SQL 文件 ), the data are as follows: The following example reads that the AGE field is greater than 25 and The OR operator means that only any one of several conditions needs to be satisfied. In Create the COMPANY table ( 下载 COMPANY SQL 文件 ), the data are as follows: The following example reads 5.18.1. AND ¶
WHERE In the clause, the syntax for using AND is as follows:SELECT column1, column2, columnN FROM table_name WHERE [condition1] AND [condition2]...AND [conditionN];
5.18.2. Example ¶
runoobdb# 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)
SALARY All records with fields greater than or equal to 65000:runoobdb=# SELECT * FROM COMPANY WHERE AGE >= 25 AND SALARY >= 65000; id | name | age | address | salary ----+-------+-----+------------+-------- 4 | Mark | 25 | Rich-Mond | 65000 5 | David | 27 | Texas | 85000 (2 rows)
5.18.3. OR ¶
WHERE In the clause, the syntax for using OR is as follows:SELECT column1, column2, columnN FROM table_name WHERE [condition1] OR [condition2]...OR [conditionN]
runoobdb# 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)
AGE Field greater than or equal to 25 or SALARY All records with fields greater than or equal to 65000:runoobdb=# SELECT * FROM COMPANY WHERE AGE >= 25 OR SALARY >= 65000; 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)