题目描述
统计出当前各个title类型对应的员工当前薪水对应的平均工资。结果给出title以及平均工资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);
解题思路
SELECT title , avg(salary) AS avg
FROM titles t
INNER JOIN salaries s
ON t.emp_no = s.emp_no
AND t.to_date = '9999-01-01'
AND s.to_date = '9999-01-01'
group by t.title
平均工资需要用avg()函数需要内连结２个表根据题意需要group by 分组title当前日期默认 ‘9999-01-01’
