개요
- SQL inner join
- SQL 내부 조인
예시 1: employee & department
SELECT * FROM employee
|
SELECT * FROM department
|
SELECT * FROM employee JOIN department
ON employee.DepartmentID = department.DepartmentID
SELECT A.LastName, B.*
FROM employee A JOIN department B
ON A.DepartmentID = B.DepartmentID
예시 2: Sales & Countries
CREATE TABLE Sales (Date date, CountryID int(11), Units int(11));
INSERT INTO Sales (Date, CountryID, Units) VALUES
('2020-01-01', 1, 40),
('2020-01-02', 1, 25),
('2020-01-03', 3, 30),
('2020-01-04', 2, 35);
CREATE TABLE Countries (ID int(11), Country varchar(16));
INSERT INTO Countries (ID, Country) VALUES
(3, 'Panama'),
(4, 'Spain');
SELECT Sales.*, Countries.Country
FROM Sales JOIN Countries
ON Sales.CountryID = Countries.ID