MySQL中多表联合数据查询

以相关的几个表中的关键行进行表的连接，以三表查询为例：

[code]create table dept_emp ( emp_no int(11) NOT NULL, dept_no char(4) NOT NULL, from_date date NOT NULL, to_date date NOT NULL, PRIMARY KEY (emp_no, dept_no));

create table emp_bonus ( emp_no int(11) NOT NULL, received datetime NOT NULL, btype smallint(5) NOT NULL);

create table employees (emp_no int(11) NOT NULL, birth_date date NOT NULL, first_name varchar(14) NOT NULL, last_name varchar(16) NOT NULL, gender char(1) NOT NULL, hire_date date NOT NULL, PRIMARY KEY (emp_no));

三表进行连接查询：

[code]select e.emp_no, dept_no, btype, received
from employees as e
inner join dept_emp as de
on e.emp_no = de.emp_no
left join emp_bonus as em
on de.emp_no = em.emp_no;