如何编写 SqlCommand 在 ASP.NET 的列中选择前 3 个重复次数最多的值

Posted 2023-05-08

【中文标题】如何编写 SqlCommand 在 ASP.NET 的列中选择前 3 个重复次数最多的值

【英文标题】：How do I write a SqlCommand that selects top 3 most repeated values in a column in ASP.NET

【发布时间】：2019-04-19 03:59:10

【问题描述】：

我正在尝试从日期选择器“从-到”格式检索最畅销的商品。我有这个SqlCommand 我正在尝试运行但它不起作用。

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个完整代码

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();
    

【参考方案1】：

您在 Select 列表中的 SOLD 列之后出现语法错误，缺少逗号 (,)，并将 order by 子句移到最后，将 where 子句移到 Group by 之前，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。

【讨论】：

我在 where 附近的语法不正确。 "关键字'WHERE'附近的语法不正确。'"

只需在SELECT 子句SELECT TOP 3 Sold, Count(Sold). 中的Sold 列之后添加一个逗号（，），并将顺序移到where 子句之后。检查更新的答案

请用您遇到的错误更新问题。另外，添加 from 和 to 日期后生成的 sql 查询是什么？

where 子句应出现在group by 之前。交换它们，其他一切都应该没问题。

【参考方案2】：

SELECT TOP 3 Sold, COUNT(Sold) AS MOST_FREQUENT 从 Transactions WHERE Dates between '"+Convert.ToDateTime(txtDate.Text)+"' 和 '"+Convert.ToDateTime(txtDate2.Text)+"' GROUP BY Sold ORDER BY COUNT(Sold) DESC

Group by 和 order by 应该在 where 子句之后。