Question

我在E/AndroidRuntime: FATAL EXCEPTION: main Process: fr.pinty, PID: 24751 java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=64206, result=-1, data=Intent { (has extras) }} to activity {fr.pinty/fr.pinty.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.Fragment.onActivityResult(int, int, android.content.Intent)' on a null object reference at android.app.ActivityThread.deliverResults(ActivityThread.java:4089) at android.app.ActivityThread.handleSendResult(ActivityThread.java:4132) at android.app.ActivityThread.-wrap20(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1533) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.Fragment.onActivityResult(int, int, android.content.Intent)' on a null object reference at fr.pinty.MainActivity.onActivityResult(MainActivity.java:92) at android.app.Activity.dispatchActivityResult(Activity.java:6932) at android.app.ActivityThread.deliverResults(ActivityThread.java:4085) at android.app.ActivityThread.handleSendResult(ActivityThread.java:4132) at android.app.ActivityThread.-wrap20(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1533) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)中有一个查询，根据该查询我找到了一些列的重复记录。

MySQL

以上查询为我提供select max(id), count(*) as cnt from table group by start_id, end_id, mysqltable having cnt>1;以及max(id)列值相同的记录数量。

我想删除与上述查询的start_id,end_id,mysqltable列匹配的所有记录

我该怎么做？

我试过以下

max(id)

但无法删除记录

Answer 1

您可以使用JOIN删除重复记录。

DELETE t1 FROM table t1
INNER JOIN
  table t2
WHERE 
t1.id > t2.id AND t1.start_id = t2.start_id AND  t1.end_id = t2.end_id AND t1.mysqltable = t2.mysqltable;

此查询保留最低ID并删除最高ID。

Answer 2

我认为这个命令应该有效：

  delete from table 
    where id in  
    ( select max(id) from table 
         group by start_id, end_id, mysqltable 
         having count(*) > 1 
    );

根据mysql中的另一个查询删除记录

2 个答案: