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  • oracle merge 目标表以及源表存在重复列的问题(转)

    SQL> select * from t_source;                                                                                             
                                                                                                                             
                                          A                                       B                                          
    --------------------------------------- ---------------------------------------                                          
                                          1                                       1                                          
                                          2                                       2                                          
                                                                                                                             
    SQL> select * from t_target;                                                                                             
                                                                                                                             
                                          A                                       B                                          
    --------------------------------------- ---------------------------------------                                          
                                          2                                      34                                          
                                          2                                    3999                                          
                                                                                                                             
    SQL> merge into t_target using t_source on (t_source.a=t_target.a) when matched then update set t_target.b=t_source.b;   
                                                                                                                             
    Done                                                                                                                     
                                                                                                                             
    SQL> select * from t_target;                                                                                             
                                                                                                                             
                                          A                                       B                                          
    --------------------------------------- ---------------------------------------                                          
                                          2                                       2                                          
                                          2                                       2                                          
                                                                                                                             
    SQL> commit;                                                                                                             
                                                                                                                             
    Commit complete                                                                                                          
                                                                                                                             
    小结:1,对于merge,目标表如果匹配列重复,但源表匹配不重复,会用源表表列新目标表的数据                                     
          2,反之,如果源表匹配列重复,此时merge就会报错,因为不知用源表哪条记录来更新目标表的数据 

     转自   

     http://blog.itpub.net/9240380/viewspace-750968/

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  • 原文地址:https://www.cnblogs.com/SamuelSun/p/6541133.html
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