SQL语句练习 自学SQL网 多表查询

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

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;