如何编写一个SqlCommand，在ASP.NET中的列中选择前3个最重复的值

Question

我试图从日期选择器“从 - 到”格式检索最畅销的项目。我有这个SqlCommand我试图运行但它不工作。

SqlCommand cmd = new SqlCommand("SELECT TOP 3 Sold COUNT(Sold) AS MOST_FREQUENT FROM Transactions GROUP BY Sold ORDER BY COUNT(Sold) DESC WHERE Dates Between'" + Convert.ToDateTime(txtDate.Text) + "' and '" + Convert.ToDateTime(txtDate2.Text) + "'", con);

更新

("SELECT TOP 3 Sold, COUNT(Sold) AS MOST_FREQUENT FROM Transactions GROUP BY Sold WHERE Dates Between '"+Convert.ToDateTime(txtDate.Text)+"' and '"+Convert.ToDateTime(txtDate2.Text)+"' ORDER BY COUNT(Sold) DESC", con);

更新2完整代码

protected void btnApply_Click(object sender, EventArgs e)
{
    string CS = ConfigurationManager.ConnectionStrings["POS_SystemConnectionString2"].ConnectionString;

    using (SqlConnection con = new SqlConnection(CS))
    {
        if (txtDate.Text != null && txtDate2.Text != null)
        {
            SqlCommand cmd = new SqlCommand("SELECT TOP 3 Sold, COUNT(Sold) AS MOST_FREQUENT FROM Transactions WHERE Sold GROUP BY Dates Between '"+Convert.ToDateTime(txtDate.Text)+"' and '"+Convert.ToDateTime(txtDate2.Text)+"' ORDER BY COUNT(Sold) DESC", con);

            con.Open();

            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            sda.Fill(dt);

            if (dt.Rows.Count != 0)
            {
                GridView1.DataSource = dt;
                GridView1.DataBind();
            }
            else
            {
            }
        }

        con.Close();
    }
}

Answer 1

您在选择列表中的SOLD列之后缺少逗号（，）的语法错误，并且还在Group by之前的end和where子句中移动order by子句，如下所示：

子句的顺序应该是SELECT，WHERE，GROUP BY，Order by

protected void btnApply_Click(object sender, EventArgs e)
        {
            string CS = ConfigurationManager.ConnectionStrings["POS_SystemConnectionString2"].ConnectionString;
            using (SqlConnection con = new SqlConnection(CS))
            {
                if (txtDate.Text != null && txtDate2.Text != null)
                {
                    SqlCommand cmd = new SqlCommand("SELECT TOP 3 Sold, COUNT(Sold) AS MOST_FREQUENT FROM Transactions WHERE Dates Between '"+Convert.ToDateTime(txtDate.Text)+"' and '"+Convert.ToDateTime(txtDate2.Text)+"'  GROUP BY Sold ORDER BY COUNT(Sold) DESC", con);

                    con.Open();
                    SqlDataAdapter sda = new SqlDataAdapter(cmd);

                    DataTable dt = new DataTable();

                    sda.Fill(dt);

                    if (dt.Rows.Count != 0)
                    {
                        GridView1.DataSource = dt;
                        GridView1.DataBind();
                    }
                    else
                    {

                    }


                }

                con.Close();

            }

此外，您必须使用参数化查询，而不是内联连接参数值以避免SQL注入。

Answer 2

SELECT TOP 3已售出，COUNT（已售出）AS MOST_FREQUENT FROM Transactions WHERE日期在'“+ Convert.ToDateTime（txtDate.Text）+”'和'“+ Convert.ToDateTime（txtDate2.Text）+”'GROUP BY Sold Ororder BY COUNT（已售出）DESC

group by和order by应该在where子句之后。