Question

我想从MySQL数据库中的一个表中选择并显示（比如在调试控制台中）所有数据。

我可以使用列名或索引读取数据，但只能在一个读取的行中读取数据。有人可以告诉我如何循环行？所以我可以阅读它的数据..

感谢您的帮助。

public class DatabaseHandler
    {
      private bool query_status;
        private int? count;
        private DataTable data_table;
        private static MySqlConnection connection;
        private MySqlDataReader data_reader;
        private MySqlCommand command;
        private static DatabaseHandler databasehandler;
    public void insert(string table, Dictionary<string, string> data)...

    public void select(string columns, string table, string where)
    {
        try
        {
            connection.Open();
            this.command = connection.CreateCommand();
            command.CommandType = CommandType.Text;
            command.CommandText = "SELECT * FROM user";
            this.data_reader = command.ExecuteReader();
            if (this.data_reader.HasRows) {
                this.count = data_reader.FieldCount;
                do
                {
                    this.data_reader.NextResult();
                    for (var i = 0; i < count; i++)
                    {
                        Debug.WriteLine(this.data_reader.GetValue(i));
//only returns one row. How to view all data?
                    }
                }
                while (this.data_reader.Read());           
            }
            connection.Close();
        }
        catch (Exception e)
        {
            Debug.WriteLine(e.Message);
        }
    }
    public void delete(string table, string where)...
    public void update(string table, string new_data, string where)... 
    public bool get_query_status()...
    public string get_custom_string()...
    public int? get_query_count()...
    public DataTable get_result()...

Answer 1

FieldCount（）返回表格中列的数量。我认为你的表只有1列，这就是为什么它不会迭代其余的记录。

我建议你删除count变量的用法，然后使用Read（）方法返回的布尔值。

Answer 2

您正在使用NextResult，这将移至下一个结果集。

请参阅Difference between SqlDataReader.Read and SqlDataReader.NextResult

在您的示例中，如果您将代码更改为

this.data_reader = command.ExecuteReader();
        if (this.data_reader.HasRows) {
            this.count = data_reader.FieldCount;
            while (this.data_reader.Read());           
            {
                for (var i = 0; i < count; i++)
                {
                    Debug.WriteLine(this.data_reader.GetValue(i));
                }
            }
           this.data_reader.Close();
        }

Answer 3

您可以使用DataReader

按顺序访问数据库记录

try
{
    connection.Open();
    MySqlCommand command = new MySqlCommand("SELECT * FROM User", connection);
    using (MySqlDataReader reader = command.ExecuteReader())
    {
        while (reader.Read())
        {
            // access your record colums by using reader
            Console.WriteLine(reader["COLUMN_NAME"]);
        }
    }
}
catch (Exception ex)
{
    // handle exception here
}
finally
{
    connection.Close();
}

或者您可以使用DataAdapter填充本地DataSet或DataTable并从那里循环您的行：

try
{
    connection.Open();
    MySqlDataAdapter adapter = new MySqlDataAdapter("SELECT * FROM User", connection);
    DataTable data = new DataTable();
    adapter.Fill(data);
    foreach (DataRow row in data.Rows)
    {
        Console.WriteLine(row["COLUMN_NAME"]);
    }
}
catch (Exception ex)
{
    throw ex;
}
finally
{
    connection.Close();
}

还要记住确保关闭所有与数据库的活动连接。

Answer 4

也许尝试使用MySqlDataAdapter：

 DataTable temp = new DataTable();
 adapter = new MySqlDataAdapter(command);
 adapter.Fill(temp);

 foreach(DataColumn column in  temp.Columns) 
 {
     foreach(DataRow row in temp.Rows)
     {
          Console.WriteLine(row[column]);
     }
 }

Answer 5

try
{
    listView1.Items.Clear();
    MySqlConnection con = new MySql.Data.MySqlClient.MySqlConnection("server=localhost;port=3306;uid=sql3305088;pwd=KwxUiLHnKt;database=sql3305088;");

    con.Open();
    MySqlCommand com = con.CreateCommand();

    com.CommandType = System.Data.CommandType.Text;
    com.CommandText = "SELECT * From eslamtarek";
    MySql.Data.MySqlClient.MySqlDataReader reader = com.ExecuteReader();


    if (reader.HasRows)
    {
        while (reader.Read())
        {
            ListViewItem lv = new ListViewItem();
            lv.Text = reader.GetString(0);
            lv.SubItems.Add(reader.GetString(1));
            lv.SubItems.Add(reader.GetString(2));
            lv.SubItems.Add(reader.GetString(3));
            lv.SubItems.Add(reader.GetString(4));
            listView1.Items.Add(lv);
        }
        reader.Close();
    }
}
catch (Exception ex)
{
    MessageBox.Show(ex.Message);
}

Answer 6

您也可以尝试这种编码方式

try
{

     DataTable data = new DataTable();

     connection.Open();
     MySqlCommand command = new MySqlCommand("SELECT * FROM User", connection);
     data.load(command.ExecuteReader());

     foreach(Datarow row in data.rows)
     {
        // access your record colums by using reader
        Console.WriteLine(row["COLUMN NAME"]);
     }

}
catch (Exception ex)
{
     // handle exception here
}
finally
{
     connection.Close();
}

C＃，mysql，如何从一个表中选择和读取所有数据？

6 个答案: