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#建立一个数据库 create database why; #新建一个用户表 create table why(employee_id bigint,name char(16),gerder enum(

#建立一个数据库
 
create database why;
 
#新建一个用户表
 
create table why(employee_id bigint,name char(16),gerder enum('M','F'),dept_id enum('caiwu','renshi','shichang','jishu'),join_time date,salary double,phone char(11),address char(40),description text);
 
#建立用户记录
 
insert into why values(20121200*(#序号),'name','F/M','caiwu/renshi/shichang/jishu','2012-10-07,*(#工资),'*'(#电话),'address','description')
 
#实现sql查询
 
    按名字查找
 
    select * from why where; #查找某个人的个人信息
 
    按照薪水>查找
 
    select * from why where salary>=3000 and salary 
    查找每个部门的人数
 
    select dent_id,count(*) as dentsum from why group by dept_id;
 
    每个部门的平均薪资
 
    select dent_id,avg(salary) as avgsalary from why group by dept_id;
 
    描述字段为空的员工
 
    select * from why where description is null; #所有信息均为空(包括用户姓名) 

    select * from why where description='';#只有描述信息为空
 
    求出每个部门女员工工资最高的职工的薪水
 
    select dept_id max(salary) from why where gerder='F' group by dept_id;
 
    名字以l开头的员工个数
 
    select * from why where name like "l%"

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