循環刪除查詢的最佳方法是什么

Question

我一直在嘗試根據數量的限制一一刪除幾行，即時通訊試圖只刪除最新的條目，但是，我想出的解決方案總是使VSHOST崩潰，是否有更好的方法來達到相同的結果？

    private void button1_Click(object sender, EventArgs e)
{
    MessageBox.Show("A apagar dados...");
    bool check = true;
    do
    {
        string connectionString;
        var path = @"C:\Users\Administrator\Desktop\connstring.txt";
        using (StreamReader sr = new StreamReader(path))
        {
            connectionString = sr.ReadLine();
        }

        var connection = new SqlConnection(connectionString);

        string queryString = string.Empty;
        using (SqlConnection deleteconnection = new SqlConnection(connectionString))
        {
            deleteconnection.Open();
            connection.Open();
            queryString = "DELETE FROM wgcdoccab WHERE numdoc = (SELECT MAX(numdoc) FROM WGCDOCCAB WHERE serie ='1' and tipodoc ='FSS' and contribuinte ='999999990' and  datadoc = CONVERT(varchar(10),dateadd(dd, -1, getdate()),120))";
            SqlCommand command = new SqlCommand(queryString, connection);
            command.ExecuteNonQuery();
            connection.Close();
        }
        using (SqlConnection deleteconnection = new SqlConnection(connectionString))
        {
            connection.Open();
            deleteconnection.Open();

            queryString = "SELECT max(numdoc) FROM wgcdoccab WHERE serie ='1' and tipodoc ='FSS' and contribuinte ='999999990' and datadoc = CONVERT(varchar(10),(dateadd(dd, -1, getdate())), 120))";
            using (SqlCommand command = new SqlCommand(queryString, connection))
            using (SqlDataReader reader = command.ExecuteReader())
            {
                if (reader.HasRows)
                {
                    check = true;
                }
                else
                {
                    check = false;
                    MessageBox.Show("Dados Apagados com sucesso");
                }
                command.Connection.Close();
            }
        }
    }
    while (check);

該代碼是相對簡單的，並且在操作結束后-變成無休止的cicle，因為它將始終為numdoc返回NULL值，我似乎找不到解決方法。 有什么建議么？

Answer 1

我不了解循環的必要性。 為什么不立即刪除所有記錄？

DELETE FROM wgcdoccab
WHERE 
    serie ='1' and
    tipodoc ='FSS' and
    contribuinte ='999999990' and
    datadoc = CONVERT(varchar(10),dateadd(dd, -1, getdate()),120))";

如果您在循環中重復查詢，它將刪除所有這些記錄，而不僅僅是最后一個。

“最后一個”到底是什么意思？ 最后2個，最后100個？ 您必須給出“最后一個”的確切定義！

假設您要刪除最后10個。 您可以通過以下查詢來實現（假設使用T-SQL）：

DELETE FROM wgcdoccab
WHERE numdoc IN (
    SELECT TOP 10 numdoc
    FROM WGCDOCCAB
    WHERE blahh blahh blahh
    ODER BY numdoc DESC
)