sql - 假设我有 max(pid)=1001 如果我想显示通过 +1 到最大值的 1002 的值，那么我该怎么做

Question

假设我有max(pid)=1001，如果我想显示 1002 的值，它通过 +1 变为最大值，那么我该怎么做

这是我想要选择 max(pid) 并希望将其显示到文本框中的整个代码

public PatientRegistration()
    {
        InitializeComponent();
        string connectionstring = "DATABASE=hmanagmentsystem;UID=root;PASSWORD=;SERVER=localhost";
        con = new MySqlConnection(connectionstring);
        con.Open();
    }

  private void PatientRegistration_Load(object sender, EventArgs e)
    {

        MySqlCommand command = new MySqlCommand("select max(pid) from patientreg",con);
        int cmd=Int32.Parse(command.ExecuteScalar().ToString());
        con.Close();

    }

Answer 1

怎么样：

MySqlCommand command = new MySqlCommand("select max(pid) + 1 from patientreg", 
    con);

更全面：

string connectionString;
public PatientRegistration()
{
    InitializeComponent();
    connectionString = "DATABASE=hmanagmentsystem;UID=root;PASSWORD=;SERVER=localhost";
}

private void PatientRegistration_Load(object sender, EventArgs e)
{
    using (SqlConnection conn = new SqlConnection(connectionString))
    {
        conn.Open;

        using (SqlCommand = new SqlCommand("select max(pid) + 1 from patientreg",conn))
        {
            // this assumes an asp:TextBox called IDTextBox
            IDTextBox.Text = command.ExecuteScalar().ToString();
        }
    }
}