Question

我一直在尝试逐个删除几行，具体取决于一定的限制，我试图只删除最新的条目但是，我想出的解决方案是不断崩溃VSHOST，是否有更好的方法来实现同样的结果？

    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);

代码相对简单，在do-while结束后，它变成了无穷无尽的cicle，因为它总是会为numdoc返回一个NULL值，我似乎找不到绕过它的方法。有什么建议吗？

Answer 1

我不明白循环的必要性。你为什么不一次删除所有记录？

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

如果你在循环中重复查询，它将删除所有这些记录，而不仅仅是最后的记录。

“最后的”究竟是什么意思？最后2个是最后100个？你必须给出“最后一个”的确切定义！

假设您要删除最后10个。您可以使用此查询（假设为T-SQL）来实现它：

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

什么是循环删除查询的最佳方式

1 个答案: