統計出當前各個title類型對應的員工當前(to_date=‘9999-01-01’)薪水對應的平均工資。結果給出title以及平均工資avg。
CREATE TABLE salaries
(
emp_no
int(11) NOT NULL,
salary
int(11) NOT NULL,
from_date
date NOT NULL,
to_date
date NOT NULL,
PRIMARY KEY (emp_no
,from_date
));
CREATE TABLE IF NOT EXISTS “titles” (
emp_no
int(11) NOT NULL,
title
varchar(50) NOT NULL,
from_date
date NOT NULL,
to_date
date DEFAULT NULL);
select a.title , avg(b.salary) as avg
from titles as a join salaries as b
on a.emp_no = b.emp_no
where a.to_date='9999-01-01' and b.to_date='9999-01-01'
group by title;