mysql 常用语句 -转

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　　http://blog.csdn.net/kakane/article/details/7401111
　　【1】建立员工档案表
   要求字段：员工员工编号，员工姓名，性别，工资，email，入职时间，部门。
【2】合理选择数据类型及字段修饰符，要求有NOT NULL，auto_increment, primary key等。
　　

    DROP TABLE IF EXISTS `workers_info`;  
CREATE TABLE `workers_info` (  
`id` int(11) NOT NULL AUTO_INCREMENT,  
`workername` varchar(20) NOT NULL,  
`sex` enum(F,M,S),  
`salary` int(11) DEFAULT '0',  
`email`  varchar(30),  
`EmployedDates`  date,  
`department`  varchar(30),  
PRIMARY KEY (`id`)  
) ENGINE=MyISAM  DEFAULT CHARSET=utf8;  
mysql> alter table workers_info ADD sex  enum('F','M','S');  
　　【3】查看表的结构
　　
　　

mysql> desc  workers_info;
　　【4】新增qq和tel字段，要求tel字段位于email前，要求入职时间是最后一个字段
　　

mysql> ALTER TABLE workers_info ADD tel varchar(15) after salary;
    mysql> ALTER TABLE workers_info ADD qq int;  
ALTER TABLE workers_info MODIFY EmployedDates date after qq;  
　　【5】把email字段修改成mailbox

ALTER TABLE workers_info CHANGE email mailbox varchar(30);
　　【6】向表里添加10条记录

mysql> INSERT INTO workers_info (workername,salary,tel,mailbox,department,qq,EmployedDates) values('xing',10000,'1598232123','xing@qq.com','yanfa',736019646,20121221);
　　【7】修改其中两条记录的tel和mailbox

    mysql> UPDATE workers_info SET mailbox = 'haha@qq.com',tel='1246543423' WHERE id = 13;  
　　【8】查看所添加记录
mysql> select * from workers_info;

【9】查看姓名和入职时间记录
 mysql> select workername,EmployedDates from workers_info;
 
【10】查询入职时间在2003年以前的

mysql> select * from workers_info where year(EmployedDates) < 2003;  
 【11】查询工资最高和最低的员工姓名

mysql> select * from workers_info ORDER BY salary limit 1;  
mysql> select * from workers_info ORDER BY salary desc limit 1;  
 【12】查询平均工资

mysql> select avg(salary) from workers_info;
　　【13】统计男员工人数、女员工人数

mysql> select count(男) from workers_info where sex="M";  
mysql> select count(女) from workers_info where sex="W";
　　【14】把email字段长度修改为255

mysql> ALTER TABLE workers_info MODIFY COLUMN email varchar(255);
　　【15】按照入职时间先后进行排序，并显示前5位员工姓名

mysql> select * from workers_info ORDER BY EmployedDates limit 5;