执行sqlite方法不起作用。需要帮助

Question

状态：有时app会顺畅运行并在tableview中显示数据库中的数据。当我重建或重新启动.. 所有数据都消失了。
我有三个文本字段和一个保存数据的按钮。
查看控制器：两个tableviews使用tableviewcontroller，另一个使用tableview delegate方法..我的代码在这里

-(IBAction)addTextToDatabase:(id)sender

{
    sqlite3_stmt * statement;
    char const * dbpath = [databasepath UTF8String];
    if (sqlite3_open(dbpath, &myDatabase) == SQLITE_OK)
    {
      NSString * insertSQL = [NSString stringWithFormat:@"INSERT INTO income (category, price, date) values (\"%@\", \"%@\", \"%@\")", self.categoryTextField.text,self.priceTextField.text,self.dateTextField.text];
        const char * insert_stmt = [insertSQL UTF8String];
        NSLog(@"%@",insertSQL);
        sqlite3_prepare_v2(myDatabase, insert_stmt,-1, &statement, NULL);if (sqlite3_step(statement)== SQLITE_DONE)
        {
            statusOfAddingToDB = [NSString stringWithFormat:@"Text Added - %@ %@ %@",self.categoryTextField.text,self.priceTextField.text,self.dateTextField.text];
      }
            else

            {
                    statusOfAddingToDB = @"Failed to Insert Databsae";
                    NSLog(@"%d",SQLITE_ERROR);
                    NSLog(@"sqlite3_step error: '%s'", sqlite3_errmsg(myDatabase));

            }

        UIAlertView * alert = [[UIAlertView alloc]initWithTitle:@"DB status" message:statusOfAddingToDB delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil];
        [alert show];

        sqlite3_finalize(statement);
        sqlite3_close(myDatabase);
    }

}

- (void)prepareDatabase
{
    // Get the documents directory
    NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docsDir = dirPaths[0];

    // Build the path to the database file
    databasepath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent:@"expenseSystem.db"]];
    NSLog(@"DB Path: %@", databasepath);

    NSFileManager * filemgr = [NSFileManager defaultManager];

    if ([filemgr fileExistsAtPath: databasepath ] == NO) {
        const char *dbpath = [databasepath UTF8String];
        if (sqlite3_open(dbpath, &myDatabase) == SQLITE_OK) {
            char *errMsg;

            NSLog(@"%s",errMsg);
            const char *sql_stmt ="CREATE TABLE IF NOT EXISTS income (id INTEGER PRIMARY KEY AUTOINCREMENT, category TEXT , price TEXT, date TEXT)";

            if (sqlite3_exec(myDatabase, sql_stmt, NULL, NULL, &errMsg) != SQLITE_OK) {
                statusOfAddingToDB = @"Failed to create table";


            } else {
                statusOfAddingToDB = @"Success in creating table";
                NSLog(@"%@",myDatabase);
            }
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"DB Status" message:statusOfAddingToDB delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
            [alert show];
            sqlite3_close(myDatabase);
        } else {
            statusOfAddingToDB = @"Failed to open/create database";
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"DB Status" message:statusOfAddingToDB delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];



            [alert show];




        }
    }
}

出现错误

  

没有表收入