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  • SQL中join的用法解析(inner join、full out join、left join)

    版权声明:本文为CSDN博主「」的原创文章,遵循 CC 4.0 BY-SA 版权协议,转载请附上原文出处链接及本声明。

    原文链接:https://blog.csdn.net/Megustas_JJC/article/details/86092980

    对于各种join情况的总结图:

    例如有如下关系的数据:

    1、inner join

     

    select * from Table_a
    join Table_b on Table_a.id_a = Table_b.id_b

     

    2.1、full outer join等于full join

     

    select * from Table_a
    full join Table_b
    on Table_a.id_a = Table_b.id_b

    2.2、full outer join but a.Key is null or b.Key is null

     

    select * from Table_a
    full outer join Table_b
    on Table_a.id_a = Table_b.id_b
    where Table_a.id_a is null or Table_b.id_b is null

    3.1、left outer join等于left join

     

    select * from Table_a
    left join Table_b on Table_a.id_a = Table_b.id_b

     

    3.2、left outer join but b.Key is null

     

    select * from Table_a

    left outer join Table_b on Table_a.id_a = Table_b.id_b

    where Table_b.id_b is null

     

    笛卡尔积
    select * from Table_a ,Table_b

    ————————————————
    版权声明:本文为CSDN博主「Megustas_JJC」的原创文章,遵循 CC 4.0 BY-SA 版权协议,转载请附上原文出处链接及本声明。
    原文链接:https://blog.csdn.net/Megustas_JJC/article/details/86092980

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  • 原文地址:https://www.cnblogs.com/youyouqiao/p/12048705.html
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