获取所有非manager的员工emp_no
CREATE TABLE dept_manager
(
dept_no
char(4) NOT NULL,
emp_no
int(11) NOT NULL,
from_date
date NOT NULL,
to_date
date NOT NULL,
PRIMARY KEY (emp_no
,dept_no
));
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
));
select emp_no from employees where emp_no not in (select emp_no from dept_manager group by emp_no)
下面来至于牛客网
先使用LEFT JOIN连接两张表,再从此表中选出dept_no值为NULL对应的emp_no记录
SELECT emp_no FROM (SELECT * FROM employees LEFT JOIN dept_manager
ON employees.emp_no = dept_manager.emp_no)
WHERE dept_no IS NULL
使用单层SELECT语句即可
SELECT employees.emp_no FROM employees LEFT JOIN dept_manager
ON employees.emp_no = dept_manager.emp_no
WHERE dept_no IS NULL