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。
AUTO INCREMENT (automatic growth) generates a unique number when a new record is inserted into the table.
PostgreSQL uses sequences to identify the self-growth of fields. The data types are smallserial, serial, and bigserial. These properties are similar to the AUTO_INCREMENT properties supported by the MySQL database.
The statements that use MySQL to set auto-growth are as follows:
CREATE TABLE IF NOT EXISTS `runoob_tbl`(
`runoob_id` INT UNSIGNED AUTO_INCREMENT,
`runoob_title` VARCHAR(100) NOT NULL,
`runoob_author` VARCHAR(40) NOT NULL,
`submission_date` DATE,
PRIMARY KEY ( `runoob_id` )
)ENGINE=InnoDB DEFAULT CHARSET=utf8;
MySQL is used AUTO_INCREMENT This property identifies the self-increment of the field.
PostgreSQL uses sequences to identify the self-growth of fields:
CREATE TABLE runoob
(
id serial NOT NULL,
alttext text,
imgurl text
)
SMALLSERIAL 、 SERIAL And BIGSERIAL Range:
Pseudo type | Storage size | Range |
|---|---|---|
| 2 byt | 1 to 32767 |
| 4 byt | 1 to 2147483647 |
| 8 byte | 1 to 922 people 337 people 2036854775807 |
5.41.1. Grammar ¶
SERIAL The basic syntax of the data type is as follows:
CREATE TABLE tablename (
colname SERIAL
);
5.41.2. Example ¶
Suppose we are going to create a COMPANY Table and create the following fields:
runoobdb=# CREATE TABLE COMPANY(
ID SERIAL PRIMARY KEY,
NAME TEXT NOT NULL,
AGE INT NOT NULL,
ADDRESS CHAR(50),
SALARY REAL
);
Now insert a few records into the table:
INSERT INTO COMPANY (NAME,AGE,ADDRESS,SALARY)
VALUES ( 'Paul', 32, 'California', 20000.00 );
INSERT INTO COMPANY (NAME,AGE,ADDRESS,SALARY)
VALUES ('Allen', 25, 'Texas', 15000.00 );
INSERT INTO COMPANY (NAME,AGE,ADDRESS,SALARY)
VALUES ('Teddy', 23, 'Norway', 20000.00 );
INSERT INTO COMPANY (NAME,AGE,ADDRESS,SALARY)
VALUES ( 'Mark', 25, 'Rich-Mond ', 65000.00 );
INSERT INTO COMPANY (NAME,AGE,ADDRESS,SALARY)
VALUES ( 'David', 27, 'Texas', 85000.00 );
INSERT INTO COMPANY (NAME,AGE,ADDRESS,SALARY)
VALUES ( 'Kim', 22, 'South-Hall', 45000.00 );
INSERT INTO COMPANY (NAME,AGE,ADDRESS,SALARY)
VALUES ( 'James', 24, 'Houston', 10000.00 );
View COMPANY The record of the table is as follows:
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