【356天】我愛刷題系列115（2018.01.27）

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1. ~

SQL習題010

1

題目描述
統計出當前各個title類型對應的員工當前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 t.title,avg(s.salary)
FROM salaries as s INNER JOIN titles as t
ON s.emp_no = t.emp_no
AND s.to_date = '9999-01-01'
AND t.to_date = '9999-01-01'
GROUP BY title