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  • inner join , left join ,right join ,full join区别

    1. Inner Join (内联接)       

     此方式返回满足第一个(顶端)输入与第二个(底端)输入联接的每一行, 即显示两表联接条件满足的记录;  

     例:  以SQL 2000 中的pubs表为例;   

            USE pubs   

            SELECT * FROM authors  AS a  INNER JOIN  publishers AS p ON a.city = p.city

            ORDER BY a.au_lname DESC  

     结果:  两个表中的所有列,但只返回联接条件满足的记录; 

     2. Left Outer Join 或 Left Join (左外联接)   

         显示左边表的所有记录,并显示联接表的所有字段满足条件的记录; 

        例: 以SQL 2000 中的pubs表为例;

            USE pubs       

            SELECT * FROM authors AS a LEFT OUTER JOIN  publishers  AS p

            ON a.city = p.city   ORDER BY p.pub_name ASC

           运行结果:

                 显示authors 表的所有记录, 并显示publishers 表的所有列的满足条件的记录;

                 此联接方式的结果正好与Right Outer Join 相反;

                 返回的记录数据为左表的记录数;

    3. Right Outer Join 或 Right Join (右外联接)

         显示右边表的所有记录,并显示左边表的所有列满足条件的记录;

         例:以SQL 2000 中的pubs 表为例;

         USE pubs

         SELECT * FROM authors AS a  RIGHT OUTER JOIN  publishers AS p

         ON  a.city = p.city  ORDER BY p.pub_name ASC

    4. Full Outer Join 或 Full Join (全外联接)

       显示联接两个表的所有列和记录;

      例: 以SQL 2000中的pubs表为例;

      USE pubs

      SELECT * FROM authors AS a FULL OUTER JOIN publishers p

      ON  a.city = p.city ORDER BY p.pub_name ASC

     

    转载出处:http://blog.csdn.net/fcjg/archive/2008/05/20/2463949.aspx

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  • 原文地址:https://www.cnblogs.com/gsk99/p/2032468.html
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