mysql 学习

创建数据库：
create database testdb;

创建表：
use testdb;
create table employees (
->empid int not null,
->AAA varchar (30),
->BBB varchar (50),
->salary float,
->primary ket (empid);    #主键索引

插入数据：
insert into employees values (1,'111','222','2322.00'),
(2,'111','222','2322.00'),
(3,'111','222','2322.00'),
(4,'111','222','2322.00');

改数据：
update employees set BBB=900 where empid = 1;  #修改empid=1行bbb列数据为900

删除数据：
delete from employees where empid = 1;

查数据：
select from employees where empid = 1；