題目描述

彙總各個部門當前員工的title型別的分配數目，結果給出部門編號dept_no、dept_name、其當前員工所有的title以及該型別title對應的數目count
CREATE TABLE `departments` (
`dept_no` char(4) NOT NULL,
`dept_name` varchar(40) NOT NULL,
PRIMARY KEY (`dept_no`));
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 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);

輸入描述:

無

輸出描述:

SELECT
	d.dept_no,
	dept.dept_name,
	t.title,
	count(d.emp_no) AS `count`
FROM
	(
		dept_emp d
		INNER JOIN titles t ON d.emp_no = t.emp_no
		AND d.to_date = '9999-01-01'
		AND t.to_date = '9999-01-01'
	)
NATURAL LEFT JOIN departments dept
GROUP BY
	d.dept_no,
	t.title;