摘要：
#等值连接： 查询员工名和对应的部门名 mysql> select last_name,department_name from employees,departments where employees.department_id=departments.department_id; 查询员工名、 阅读全文
摘要：
常见函数： mysql> select sum(salary) from employees; + + | sum(salary) | + + | 691400.00 | + + 1 row in set (0.00 sec) mysql> select avg(salary) from emplo 阅读全文