目录

Day 6 用JOINs进行多表联合查询

Day 7 外连接 OUTER JOINs

Day 8 外连接 特殊关键字 NULLs

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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 moviesON movies.id=boxoffice.Movie_idWHERE Domestic_sales<International_sales;SELECT * FROM BoxofficeINNER JOIN moviesON movies.id=boxoffice.Movie_idORDER BY Rating ASCSELECT Director , International_sales FROM Boxoffice   INNER JOIN movieson movies.id=boxoffice.Movie_idORDER BY International_sales DESC LIMIT 1 OFFSET 0;SELECT Director , International_sales FROM Boxoffice INNER JOIN moviesON movies.id=boxoffice.Movie_idORDER BY International_sales DESCLIMIT 1 OFFSET 0;

Day 7 外连接 OUTER JOINs

SELECT DISTINCT Building_name FROM buildings LEFT JOIN employees  WHERE employees.Building=buildings .Building_nameSELECT DISTINCT Role ,Building_name FROM buildings LEFT JOIN employees   on employees.Building=buildings .Building_name;SELECT DISTINCT Building ,Capacity FROM buildings LEFT JOIN employeesON employees .Building = buildings.Building_nameWHERE Building is not null;

Day 8 外连接 特殊关键字 NULLs

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SELECT Role ,Name FROM employeesWHERE Building IS NULL;select * FROM BuildingsLEFT JOIN EmployeesON Buildings.Building_name = Employees.Building	WHERE name is null;