Error while updating sqlite row in ios

I'm getting "error while updating row" error when I'm trying to update sqlite row in iOS. Here is my update method:

-(BOOL) updateResultForLesson:(int)lessonId result:(int)result{
    const char *dbpath = [databasePath UTF8String];
    if (sqlite3_open(dbpath, &database) == SQLITE_OK)
    {

        sqlite3_stmt *statement;
        NSString *querySQL = [NSString stringWithFormat:@"update lessons set result=%d where id=%d",result, lessonId];

        const char *query_stmt = [querySQL UTF8String];

        sqlite3_prepare_v2(database, query_stmt, -1, &statement, NULL);


        if (sqlite3_step(statement) == SQLITE_DONE)
        {
            NSLog(@"updated");
        return YES;
        }
        else {
            sqlite3_reset(statement);
            NSLog(@"error while updating row");
            return NO;
        }
    }
    return NO;

}

and here insert method which works fine:

-(BOOL) addLesson:(NSString *)title levelId:(NSInteger)levelId categoryId:(NSInteger)categoryId{
    const char *dbpath = [databasePath UTF8String];
    if (sqlite3_open(dbpath, &database) == SQLITE_OK)
    {
        int result = 0;

        NSString *insertSQL = [NSString stringWithFormat:@"insert into lessons (title, level_id, category_id, result) values(\"%@\", \"%d\", \"%d\", \"%d\")",title, levelId, categoryId, result];

        const char *insert_stmt = [insertSQL UTF8String];
        sqlite3_prepare_v2(database, insert_stmt,-1, &statement, NULL);

        if (sqlite3_step(statement) == SQLITE_DONE)
        {
           ;
            return YES;
        }
        else {
            sqlite3_reset(statement);
            return NO;
        }
    }
    return NO;

}

what am I doing wrong? can anyone help? Insert and select methods works well, I have only problem with updating rows.