android - Column not found in SQLite databse -

i reated column name called _id, when run , view database in listview using getallrows() method, shows error saying (no such column: _id (code 1): , while compiling: select distinct _id, eventtitle, date, destination, durationtime, alarmtime event.).
below code , error message.
please me , teach happen code.

public class dbhandler{  private static final string tag = "dbhandler";  //field names public static final string column_id = "_id"; public static final string column_eventtitle = "eventtitle"; public static final string column_date = "date"; public static final string column_destination = "destination"; public static final string column_duration = "durationtime"; public static final string column_alarmtime = "alarmtime"; public static final string[] all_keys = new string[]{column_id, column_eventtitle, column_date, column_destination, column_duration,column_alarmtime};  //column number each field name: public static final int col_id = 0; public static final int col_eventtitle = 1; public static final int col_date = 2; public static final int col_destination = 3; public static final int col_duration = 4; public static final int col_alarmtime = 5;  //database info: private static final int database_version = 2; private static final string database_name = "sp"; public static final string table_event = "event";   //sql statament create database private static final string database_create_sql =         "create table " + table_event + "(" +         column_id + " integer primary key autoincrement, " +         column_eventtitle + " text not null, " +         column_date + " text not null, " +         column_destination + " text not null, " +         column_duration + " text not null, " +         column_alarmtime + " text not null" +         ");";  private final context context; private databasehelper mydbhelper; private sqlitedatabase db;   public dbhandler(context ctx){     this.context = ctx;     mydbhelper = new databasehelper(context); }  public dbhandler open(){     db = mydbhelper.getwritabledatabase();     return this; }  public void close(){     mydbhelper.close(); }   public long insertevent(string eventtitle, string date, string destination, string duration, string alarmtime){     contentvalues contentvalues = new contentvalues();     contentvalues.put(column_eventtitle, eventtitle);     contentvalues.put(column_date, date);     contentvalues.put(column_destination, destination);     contentvalues.put(column_duration, duration);     contentvalues.put(column_alarmtime, alarmtime);      //insert data database     return db.insert(table_event, null, contentvalues);  }  //delete row database, rowid (primary key) public boolean deleterow(long rowid){     string = column_id + "=" + rowid;     return db.delete(table_event, where, null) != 0; }  //return data in database public cursor getallrows(){     string = null;     cursor c = db.query(true, table_event, all_keys, where, null, null, null,null, null);     if(c != null){         c.movetofirst();     }     return c; }  //get specific row(by rowid) public cursor getrow(long rowid){     string = column_id + "=" + rowid;     cursor c = db.query(true, table_event, all_keys, where, null, null, null, null, null);     if(c != null){         c.movetofirst();     }     return c; }  //change existing row equal new data public boolean updateevent(long id, string eventtitle, string date, string destination, string duration,string alarmtime ){     string = column_id + "=" + id;     contentvalues newvalues = new contentvalues();     newvalues.put(column_eventtitle, eventtitle);     newvalues.put(column_date, date);     newvalues.put(column_destination, destination);     newvalues.put(column_duration, duration);     newvalues.put(column_alarmtime, alarmtime);     return db.update(table_event, newvalues, where, null) !=0; }   private static class databasehelper extends sqliteopenhelper{     databasehelper(context context){         super(context, table_event, null, database_version);     }      @override     public void oncreate(sqlitedatabase db){         db.execsql(database_create_sql);     }      @override     public void onupgrade(sqlitedatabase db, int oldversion, int newversion){         log.w(tag, "upgrading application's database version" + oldversion +         "to" + newversion + ", destroy old data!");          //destroy old database:         db.execsql("drop table if exists" + table_event);          oncreate(db);     } } } 

error:

android.database.sqlite.sqliteexception: no such column: _id (code 1): , while compiling: select distinct _id, eventtitle, date, destination, durationtime, alarmtime event             @ android.database.sqlite.sqliteconnection.nativepreparestatement(native method)             @ android.database.sqlite.sqliteconnection.acquirepreparedstatement(sqliteconnection.java:1113)             @ android.database.sqlite.sqliteconnection.prepare(sqliteconnection.java:690)             @ android.database.sqlite.sqlitesession.prepare(sqlitesession.java:588)             @ android.database.sqlite.sqliteprogram.<init>(sqliteprogram.java:58)             @ android.database.sqlite.sqlitequery.<init>(sqlitequery.java:37)             @ android.database.sqlite.sqlitedirectcursordriver.query(sqlitedirectcursordriver.java:44)             @ android.database.sqlite.sqlitedatabase.rawquerywithfactory(sqlitedatabase.java:1430)             @ android.database.sqlite.sqlitedatabase.querywithfactory(sqlitedatabase.java:1277)             @ android.database.sqlite.sqlitedatabase.query(sqlitedatabase.java:1148)             @ com.howard.fyp.dbhandler.getallrows(dbhandler.java:92)             @ com.howard.fyp.todayactivity.populatelistview(todayactivity.java:40)             @ com.howard.fyp.todayactivity.oncreateview(todayactivity.java:26)             @ android.support.v4.app.fragment.performcreateview(fragment.java:1786)             @ android.support.v4.app.fragmentmanagerimpl.movetostate(fragmentmanager.java:953)             @ android.support.v4.app.fragmentmanagerimpl.movetostate(fragmentmanager.java:1136)             @ android.support.v4.app.backstackrecord.run(backstackrecord.java:739)             @ android.support.v4.app.fragmentmanagerimpl.execpendingactions(fragmentmanager.java:1499)             @ android.support.v4.app.fragmentmanagerimpl$1.run(fragmentmanager.java:456)             @ android.os.handler.handlecallback(handler.java:733)             @ android.os.handler.dispatchmessage(handler.java:95)             @ android.os.looper.loop(looper.java:157)             @ android.app.activitythread.main(activitythread.java:5356)             @ java.lang.reflect.method.invokenative(native method)             @ java.lang.reflect.method.invoke(method.java:515)             @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:1265)             @ com.android.internal.os.zygoteinit.main(zygoteinit.java:1081)             @ dalvik.system.nativestart.main(native method) 

did add _id column in second time?
have increase database_version constant value in order make onupgrade() method fire.

but onupgrade() method fails destroying old table:

db.execsql("drop table if exists" + table_event); 

you need space before table name:

db.execsql("drop table if exists " + table_event); 

or, since old table still there, won't create new one.