消除重复的SQL？

如何消除重复项？它必须是10行，显示每个学生ID（1x）。我试过这2种不同的方式。（见下文）（共同项目是类标识码）消除重复的SQL？

SQL> select distinct(student_id),event.class_id, event.event_id, event.event_name 
    2 from student_class 
    3 inner join event on event.class_id = student_class.class_id 
    4 where student_class.class_id = '10' 
    5 order by student_id desc; 

STUDENT_ID CLASS_ID EVENT_ID EVENT_NAME 
---------- ---------- ---------- -------------------------------------------------- 
     20   10   5 PICKUP SOCCER GAME 
     20   10   2 Flag FOOtball Game 
     18   10   2 Flag FOOtball Game 
     18   10   5 PICKUP SOCCER GAME 
     16   10   2 Flag FOOtball Game 
     16   10   5 PICKUP SOCCER GAME 
     12   10   5 PICKUP SOCCER GAME 
     12   10   2 Flag FOOtball Game 
     9   10   5 PICKUP SOCCER GAME 
     9   10   2 Flag FOOtball Game 
     8   10   2 Flag FOOtball Game 
     8   10   5 PICKUP SOCCER GAME 
     6   10   2 Flag FOOtball Game 
     6   10   5 PICKUP SOCCER GAME 
     4   10   5 PICKUP SOCCER GAME 
     4   10   2 Flag FOOtball Game 
     3   10   2 Flag FOOtball Game 
     3   10   5 PICKUP SOCCER GAME 
     2   10   5 PICKUP SOCCER GAME 
     2   10   2 Flag FOOtball Game 

SQL> select distinct(student_id), student_class.class_id, 
    event.event_id, event.event_date_time 
    from student_class 
    inner join event on event.class_id = student_class.class_id 
    order by student_id desc; 

STUDENT_ID CLASS_ID EVENT_ID EVENT_DAT 
---------- ---------- ---------- --------- 
     22   9   1 09-NOV-99 
     21   2   6 20-NOV-99 
     21   9   1 09-NOV-99 
     20   9   1 09-NOV-99 
     20   10   2 19-JAN-99 
     20   10   5 09-JUL-99 
     18   9   1 09-NOV-99 
     18   10   2 19-JAN-99 
     18   10   5 09-JUL-99 
     17   9   1 09-NOV-99 
     16   2   6 20-NOV-99 
     16   9   1 09-NOV-99 
     16   10   2 19-JAN-99 
     16   10   5 09-JUL-99 
     15   9   1 09-NOV-99 
     14   9   1 09-NOV-99 
     13   9   1 09-NOV-99 
     12   2   6 20-NOV-99 
     12   9   1 09-NOV-99 
     12   10   2 19-JAN-99 
     12   10   5 09-JUL-99 
     11   2   6 20-NOV-99 
     11   9   1 09-NOV-99 
     9   10   2 19-JAN-99 
     9   10   5 09-JUL-99 
     8   2   6 20-NOV-99 
     8   10   2 19-JAN-99 
     8   10   5 09-JUL-99 
     7   2   6 20-NOV-99 
     6   10   2 19-JAN-99 
     6   10   5 09-JUL-99 
     4   10   2 19-JAN-99 
     4   10   5 09-JUL-99 
     3   10   2 19-JAN-99 
     3   10   5 09-JUL-99 
     2   2   6 20-NOV-99 
     2   9   1 09-NOV-99 
     2   10   2 19-JAN-99 
     2   10   5 09-JUL-99

来源

2013-10-04 Brian Wilson

喜花花公子做到这一点，不明白你的问题，你能举一些样品吗？ –

在我看来，'EVENTS'表有两个class_id = 10的event_id，这就是你在输出中为每个student_id获取两行的方式 – Incognito

您可以通过以下方法

create table table_name2 as select distinct * from table_name1; 
drop table table_name1; 
rename table_name2 to table_name1;

或通过此查询

DELETE FROM table_name A WHERE ROWID > (SELECT min(rowid) FROM table_name B WHERE  A.key_values = B.key_values);

来源

2013-10-04 04:33:49

消除重复的SQL？

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