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mysql 主键自动增长

Jun 07, 2016 pm 03:47 PM
mysql primary key increase definition identifier automatic

1、把主键定义为自动增长标识符类型 在mysql中,如果把表的主键设为auto_increment类型,数据库就会自动为主键赋。例如: create table customers(id int auto_increment primary key not null, name varchar(15)); insert into customers(name) values(name

1、把主键定义为自动增长标识符类型

在mysql中,如果把表的主键设为auto_increment类型,数据库就会自动为主键赋值。例如:

create table customers(id int auto_increment primary key not null, name varchar(15));

insert into customers(name) values("name1"),("name2");

一旦把id设为auto_increment类型,mysql数据库会自动按递增的方式为主键赋值。

在MS SQLServer中,如果把表的主键设为identity类型,数据库就会自动为主键赋值。例如:

create table customers(id int identity(1,1) primary key not null, name varchar(15));

insert into customers(name) values("name1"),("name2");

select id from customers;

查询结果和mysql的一样。由此可见,一旦把id设为identity类型,MSSQLServer数据库会自动按递增的方式为主键赋
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