mysql 基本操作练习
1 create table employee (name varchar(30), sex char(2), age int, address varchar(30)); 2 3 insert into employee values ('张三', '女', 19, '北京'); 4 insert into employee values ('李四', '男', 20, '上海'); 5 insert into employee values ('王五', '女', 25, '广州'); 6 insert into employee values ('薛六', '女', 20, '北京'); 7 insert into employee values ('王五', '男', 22, '北京'); 8 insert into employee values ('赵七', '男', 28, '上海'); 9 insert into employee values ('张四', '女', 23, '北京'); 10 11 #(1). 写出sql语句,查询所有年龄大于20岁的员工(2分) 12 select *from employee where age>20; 13 #(2). 写出sql语句,查询所有年龄小于25岁的女性员工(3分) 14 select *from employee where sex='女' and age<25; 15 #(3). 写出sql语句,统计男女员工各有多少名(3分) 16 #count 函数 17 select count(*) from employee;#统计表元素个数 18 select count(*) from employee where sex='女';#统计女生个数 19 select sex,count(*) from employee group by sex;#group by sex 按性别分组,用性别标记分组 20 select sex,count(*) as num from employee group by sex;#as 起别名 21 22 #(4). 写出sql语句,按照年龄倒序获取员工信息(3分) 23 select * from employee order by age desc; 24 #(5). 写出sql语句,获取员工中哪个姓名具有重名现象(3分) 25 SELECT * 26 FROM employee 27 WHERE name IN (SELECT name 28 FROM employee 29 GROUP BY name 30 HAVING COUNT(*) > 1) 31 #(6). 写出sql语句,查询所有姓张的员工(3分) 32 select * from employee where name like '%张%';#模糊查询,只要含张字 33 select * from employee where name like '张%';#只要姓张 34 #占位符写法 35 select * from employee where name like '张__'; 36 #(7). 写出sql语句,查询住址为北京的前3条记录(3分) 37 select * from employee where address='北京' order by name asc limit 0,3;#从下标几开始 ,几个 38 select * from employee limit 3,3; 39 #(8). 写出sql语句,查询员工总数(3分) 40 select count(*) as allnum from employee; 41 #(9). 写出sql语句,向表中插入一条记录(2分) 42 insert into employee(name,sex,age,address) values('七七','男',20,'深圳'); 43 #(10).写出sql语句,修改员工张四的住址为南京(2分) 44 update employee set address='南京' where name='张四'; 45 #(11).写出sql语句,删除年龄大于24岁的女员工(2分) 46 delete from employee where age>24 and sex='女';