Ndtyjky

Activity Code

String MMS = "(SELECT Name FROM UserData WHERE MessagesSent=(SELECT max(MessagesSent) FROM UserData))";

db.execSQL("UPDATE MainData SET MostMessagesSent = "+ MMS + "+ WHERE Data = MyData");

Im not sure about the code but this is is the onCreate of an activity... WIll the changes take place using this code?

Is it the correct method?

I hope the query is understandable...

Error

 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.database.sqlite.SQLiteDatabase.execSQL(java.lang.String)' on a null object reference

                                                   at com.appmaster.akash.messageplus.Settings.UsageSettings.onCreateView(UsageSettings.java:43)

                                                   at android.support.v4.app.Fragment.performCreateView(Fragment.java:2354)

                                                   at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1419)

                                                   at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1740)

                                                   at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1809)

                                                   at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:799)

                                                   at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2580)

                                                   at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2367)

                                                   at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)

                                                   at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2229)

                                                   at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:700)

                                                   at android.os.Handler.handleCallback(Handler.java:742)

                                                   at android.os.Handler.dispatchMessage(Handler.java:95)

                                                   at android.os.Looper.loop(Looper.java:157)

                                                   at android.app.ActivityThread.main(ActivityThread.java:5571)

                                                   at java.lang.reflect.Method.invoke(Native Method)

                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:745)

                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:635)

If db is properly initialized, with this line:

db.execSQL("UPDATE MainData SET MostMessagesSent = "+ MMS + "+ WHERE Data = MyData");

you want to execute an UPDATE statement that will update the column MostMessagesSent of table MainData with a value fetched from the query strored in the variable MMS:

String MMS = "(SELECT Name FROM UserData WHERE MessagesSent=(SELECT max(MessagesSent) FROM UserData))";

In order for this to work you must have initialized properly the db object.

I suppose you have a class extending SQLiteOpenHelper which provides the initialization of db.

Also the names of the tables and columns must match the intended behavior.

The problem is that execSQL() does not return a value indicating that the update was successful or not.
You have to check it yourself.