Question

以下方法应检查表中是否已存在记录或否。但是，我收到语法错误＆＃34; 没有这样的列＆＃34;。

 public void ifExist(int myId)
 {
     string dbPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Personal), "ormdemo.db3");
     var db = new SQLiteConnection(dbPath);
     SQLiteCommand cmd = new SQLiteCommand(db);
     cmd.CommandText = "SELECT count(*) FROM storeConsumption WHERE Id = ?"+ myId;

     int count = Convert.ToInt32(cmd.ExecuteScalar<storeConsumption>());
     if (count == 0)
     {
         Console.WriteLine("The record is NOT Existed");    
     }
     else
     {
         Console.WriteLine("The record is Existed");
     }
 }

虽然，仍有同样的错误。如果你知道如何解决它，我将感激不尽？

更新：我可以像这样解决这个问题：

public async Task<Boolean>  ifExist(int id){

    var result = await sdb.databaseConnection().ExecuteScalarAsync<int>("SELECT count(*) FROM storeConsumption WHERE Id = ?", id);
    Console.WriteLine(result);
    if (result > 0) return true;

    return false;

}

Answer 1

似乎由“Id =？”引起。如果要添加参数，请尝试使用以下命令行

cmd.CommandText =“SELECT count（*）FROM storeConsumption WHERE Id = @myId”; cmd.Parameters.Add（ “@ MYID”，MYID）;

更多信息： https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.commandtext(v=vs.110).aspx

Answer 2

更新：以下代码已经解决了错误并且运行良好：

public async Task<Boolean>  ifExist(int id){

    var result = await sdb.databaseConnection().ExecuteScalarAsync<int>("SELECT count(*) FROM storeConsumption WHERE Id = ?", id);
    Console.WriteLine(result);
    if (result > 0) return true;

    return false;

}

sqlite异常没有这样的列

2 个答案: