mysql主键基本操作SQL

--创建表
DROP TABLE IF EXISTS `employee_base_info`;
CREATE TABLE `employee_base_info` (
`employee_no` varchar(32) NOT NULL COMMENT '员工编号',
`employee_name` varchar(32) DEFAULT NULL COMMENT '员工姓名',
`entry_date` varchar(2) DEFAULT NULL COMMENT '入职时间',
`create_time` datetime NOT NULL COMMENT '创建时间',
`update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',
PRIMARY KEY (`employee_no`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='员工基本信息表';

--删除主键
alter table employee_base_info drop primary key;

--创建主键
alter table employee_base_info add primary key(employee_no);

--重建主键
alter table employee_base_info drop primary key, add primary key(`employee_no`,`entry_date`);