目录
[Day 6 用JOINs进行多表联合查询](#Day 6 用JOINs进行多表联合查询)
[Day 7 外连接 OUTER JOINs](#Day 7 外连接 OUTER JOINs)
[Day 8 外连接 特殊关键字 NULLs](#Day 8 外连接 特殊关键字 NULLs)
Day 6 用JOINs进行多表联合查询


SELECT * FROM Boxoffice
INNER JOIN movies
ON movies.id=boxoffice.Movie_id;
SELECT * FROM Boxoffice
INNER JOIN movies
ON movies.id=boxoffice.Movie_id
WHERE Domestic_sales<International_sales;
SELECT * FROM Boxoffice
INNER JOIN movies
ON movies.id=boxoffice.Movie_id
ORDER BY Rating ASC
SELECT Director , International_sales FROM Boxoffice
INNER JOIN movies
on movies.id=boxoffice.Movie_id
ORDER BY International_sales DESC
LIMIT 1 OFFSET 0;
SELECT Director , International_sales FROM Boxoffice
INNER JOIN movies
ON movies.id=boxoffice.Movie_id
ORDER BY International_sales DESC
LIMIT 1 OFFSET 0;
Day 7 外连接 OUTER JOINs


SELECT DISTINCT Building_name FROM buildings
LEFT JOIN employees
WHERE employees.Building=buildings .Building_name
SELECT DISTINCT Role ,Building_name FROM buildings
LEFT JOIN employees
on employees.Building=buildings .Building_name;
SELECT DISTINCT Building ,Capacity FROM buildings
LEFT JOIN employees
ON employees .Building = buildings.Building_name
WHERE Building is not null;
Day 8 外连接 特殊关键字 NULLs

·

SELECT Role ,Name FROM employees
WHERE Building IS NULL;
select * FROM Buildings
LEFT JOIN Employees
ON Buildings.Building_name = Employees.Building
WHERE name is null;