服务器 频道

如何使用SQL--JOIN之完全用法的具体说明

  使用右向外联接
  假设在 city 列上联接 authors 表和 publishers 表。结果只显示在出版商所在城市居住的作者(本例中为 Abraham Bennet 和 Cheryl Carson)。SQL-92 右向外联接运算符 RIGHT OUTER JOIN 指明:不管第一个表中是否有匹配的数据,结果将包含第二个表中的所有行。
  
  若要在结果中包括所有的出版商,而不管城市中是否还有出版商居住,请使用 SQL-92 右向外联接。下面是 Transact-SQL 右向外联接的查询和结果:
  
  USE pubs
  SELECT a.au_fname, a.au_lname, p.pub_name
  FROM authors AS a RIGHT OUTER JOIN publishers AS p
  ON a.city = p.city
  ORDER BY p.pub_name ASC, a.au_lname ASC, a.au_fname ASC
  
  下面是结果集:
  
  au_fname au_lname pub_name
  -------------------- ------------------------ --------------------
  Abraham Bennet Algodata Infosystems
  Cheryl Carson Algodata Infosystems
  NULL NULL Binnet & Hardley
  NULL NULL Five Lakes Publishing
  NULL NULL GGG&G
  NULL NULL Lucerne Publishing
  NULL NULL New Moon Books
  NULL NULL Ramona Publishers
  NULL NULL Scootney Books
  
  (9 row(s) affected)
  
  使用谓词(如将联接与常量比较)可以进一步限制外联接。下例包含相同的右向外联接,但消除销售量低于 50 本的书籍的书名:
  
  USE pubs
  SELECT s.stor_id, s.qty, t.title
  FROM sales s RIGHT OUTER JOIN titles t
  ON s.title_id = t.title_id
  AND s.qty > 50
  ORDER BY s.stor_id ASC
  
  下面是结果集:
  
  stor_id qty title
  ------- ------ ---------------------------------------------------------
  (null) (null) But Is It User Friendly?
  (null) (null) Computer Phobic AND Non-Phobic Individuals: Behavior
  Variations
  (null) (null) Cooking with Computers: Surreptitious Balance Sheets
  (null) (null) Emotional Security: A New Algorithm
  (null) (null) Fifty Years in Buckingham Palace Kitchens
  7066 75 Is Anger the Enemy?
  (null) (null) Life Without Fear
  (null) (null) Net Etiquette
  (null) (null) Onions, Leeks, and Garlic: Cooking Secrets of the
  Mediterranean
  (null) (null) Prolonged Data Deprivation: Four Case Studies
  (null) (null) Secrets of Silicon Valley
  (null) (null) Silicon Valley Gastronomic Treats
  (null) (null) Straight Talk About Computers
  (null) (null) Sushi, Anyone?
  (null) (null) The Busy Executive''s Database Guide
  (null) (null) The Gourmet Microwave
  (null) (null) The Psychology of Computer Cooking
  (null) (null) You Can Combat Computer Stress!
  
  (18 row(s) affected)
  
  有关谓词的更多信息,请参见 WHERE。
  
0
相关文章