在数据库连接和查询代码方面需要帮助

Question

在我下面的代码中，cmdquery 有效，但 hrquery 无效。如何获得另一个查询来填充网格视图？我需要建立新的连接还是使用相同的连接？你们能帮帮我吗？我是 C# 和 asp 的新手。这是我放在一起的一些意大利面条代码。这可能都是错误的，所以如果您有更好的方法，请随时分享。

if (Badge != String.Empty)
{
    string cmdquery = "SELECT * from Employees WHERE Badge ='" + Badge + "'";
    string hrquery = "SELECT CLOCK_IN_TIME, CLOCK_OUT_TIME FROM CLOCK_HISTORY   WHERE Badge ='" + Badge + "'";

    OracleCommand cmd = new OracleCommand(cmdquery);
    cmd.Connection = conn;
    cmd.CommandType = CommandType.Text;
    conn.Open();

    OracleDataReader reader = cmd.ExecuteReader();

    while (reader.Read())
    {
        this.xUserNameLabel.Text += reader["EMPLOYEE_NAME"];
        this.xDepartmentLabel.Text += reader["REPORT_DEPARTMENT"];               
    }

    OracleCommand Hr = new OracleCommand(hrquery);
    Hr.Connection = conn;
    Hr.CommandType = CommandType.Text;

    OracleDataReader read = Hr.ExecuteReader();

    while (read.Read())
    {
        xHoursGridView.DataSource = hrquery;
        xHoursGridView.DataBind();
    }
}
conn.Close();

Answer 1

您的数据访问代码通常应如下所示：

string sql = "SELECT * FROM Employee e INNER JOIN Clock_History c ON c.Badge = e.Badge WHERE e.Badge = @BadgeID";
using (var cn = new OracleConnection("your connection string here"))
using (var cmd = new OracleCommand(sql, cn))
{
    cmd.Parameters.Add("@BadgeID", OracleDbType.Int).Value = Badge;

    cn.Open();

    xHoursGridView.DataSource = cmd.ExecuteReader();
    xHoursGridView.DataBind();
}

请注意，这只是通用模板。您需要根据您的确切需求对其进行一些调整。从中获取的重要内容是 using 块以正确创建和处置您的连接对象以及防止 sql 注入的参数。

关于连接问题，也有例外，但您通常一次只能将连接用于一个活动结果集。因此，您可以重复使用原始代码中的相同 conn 对象，但前提是您必须在上一个命令中完全完成它之后。如果需要，也可以打开两个连接。但是，最好的选项是尽可能将相关查询合并到单个 sql 语句中。

Answer 2

我什至不打算讨论你应该如何使用usings 和方法：p

if (Badge != String.Empty)
    {

        string cmdquery = "SELECT * from Employees WHERE Badge ='" + Badge + "'";
        string hrquery = "SELECT CLOCK_IN_TIME, CLOCK_OUT_TIME FROM CLOCK_HISTORY   WHERE Badge ='" + Badge + "'";

        OracleCommand cmd = new OracleCommand(cmdquery);
        cmd.Connection = conn;
        cmd.CommandType = CommandType.Text;
        conn.Open();

        OracleDataReader reader = cmd.ExecuteReader();


            while (reader.Read())
            {
                this.xUserNameLabel.Text += reader["EMPLOYEE_NAME"];
                this.xDepartmentLabel.Text += reader["REPORT_DEPARTMENT"];

            }


            OracleCommand Hr = new OracleCommand(hrquery);
            Hr.Connection = conn;
            Hr.CommandType = CommandType.Text;


            OracleDataReader read = Hr.ExecuteReader();

            //What's this next line? Setting the datasource automatically
            // moves through the data.
            //while (read.Read())
            //{
                                          //I changed this to "read", which is the
                                          //datareader you just created.
                xHoursGridView.DataSource = read;
                xHoursGridView.DataBind();
            //}


    }
    conn.Close();