Database Query not working

The following is my table :

db.execSQL("CREATE TABLE "+ callTable+" ("+ colID + " INTEGER PRIMARY KEY AUTOINCREMENT, "+ colPhNum + " TEXT, " + colDur + " INTEGER, "
           + colDate + " INTEGER, " + colDay + " TEXT, " + colYear + " INTEGER, " + colType + " TEXT, " + colStTime + " TEXT, " + colHour + " INTEGER, " + colMonth +  " INTEGER)");开发者_如何学运维

and I am trying to get execute this query :

SQLiteDatabase db=this.getWritableDatabase();

String j = "SELECT " + colPhNum + "," + "SUM(" +colDur +") FROM " + callTable +" WHERE " + colYear + "=" + y+ " AND " +colMonth +"=" + m + " AND " +colDate + "=" + d + " AND " + colHour + ">" + h
         + " GROUP BY " + colPhNum;

Cursor c = db.rawQuery(j,null);
c.close();
return c;

But this is not working. This is the error log:

D/AndroidRuntime(  209): Shutting down VM
W/dalvikvm(  209): threadid=3: thread exiting with uncaught exception (group=0x4001b188)
E/AndroidRuntime(  209): Uncaught handler: thread main exiting due to uncaught exception
E/AndroidRuntime(  209): java.lang.IllegalStateException: attempt to acquire a reference on a close SQLiteClosable
E/AndroidRuntime(  209):    at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:31)
E/AndroidRuntime(  209):    at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:69)
E/AndroidRuntime(  209):    at  android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:288)
E/AndroidRuntime(  209):    at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:269)

Please help.

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Before the query add below code and try

db = openOrCreateDatabase( "databasename.db" , SQLiteDatabase.CREATE_IF_NECESSARY , null );