mysql数据库的一些简单的sql语句 内连接 - 表的关联查询

# 创建一个user表create table users(    id int primary key auto_increment,    name varchar(20),    dpt_id int);# 向user表中插入数据insert into users values    (null,'刘备',1),    (null,'关羽',2),    (null,'赵飞',2),    (null,'吕布',2),    (null,'小乔',3),    (null,'大乔',3);# 创建一个department表create table department(    id int primary key auto_increment,    name varchar(20));# 向department表中插入数据insert into department values    (null,'指挥部'),    (null,'作战部'),    (null,'后勤部');# 查询 users 表中的第三和第四条数据 (第一个数字是偏移量，第二个数字是查询几条)select * from users limit 2,2;# 为users表取别名select u.name from users as u;# 为users表中的字段取别名select name as '姓名', dpt_id as '部门' from users;# 表的关联查询 查询users表中员工的姓名和所在的部门select u.name as '姓名',d.name as '部门' from users as u inner join department as d where u.dpt_id = d.id;# 表的关联查询 查询users表中吕布所在的部门 (on 可以换成 where)select d.name from department as d inner join users as u on u.dpt_id=d.id and u.name='吕布';