【363天】我愛刷題系列122（2018.02.03）

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1. ~

SQL習題017

1

題目描述
獲取全部非manager員工當前的薪水狀況，給出dept_no、emp_no以及salary ，當前表示to_date='9999-01-01'
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 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));
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));

一、先用INNER JOIN鏈接employees和salaries，找出當前全部員工的工資狀況
二、再用INNER JOIN鏈接dept_emp表，找到全部員工所在的部門
三、最後用限制條件de.emp_no NOT IN (SELECT emp_no FROM dept_manager WHERE to_date = '9999-01-01')選出當前全部非manager員工，再依次輸出dept_no、emp_no、salary

SELECT de.dept_no, s.emp_no, s.salary 
FROM (employees AS e INNER JOIN salaries AS s ON s.emp_no = e.emp_no AND s.to_date = '9999-01-01')
INNER JOIN dept_emp AS de ON e.emp_no = de.emp_no
WHERE de.emp_no NOT IN (SELECT emp_no FROM dept_manager WHERE to_date = '9999-01-01')
此外，還能做以下簡化，不鏈接employees表也能完成：

SELECT de.dept_no, s.emp_no, s.salary 
FROM dept_emp AS de INNER JOIN salaries AS s ON s.emp_no = de.emp_no AND s.to_date = '9999-01-01'
WHERE de.emp_no NOT IN (SELECT emp_no FROM dept_manager WHERE to_date = '9999-01-01')