c# - C#中的sql命令错误

Question

我编写这段代码是为了从数据库中的两个表中检索一些信息。但是当我运行它时，我得到了这个错误

Column 'Eaten_food.Cardserial' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

代码:

 private void button8_Click(object sender, EventArgs e)
 {
        using (SqlConnection con = new SqlConnection(WF_AbsPres_Food.Properties.Settings.Default.DbConnectionString))
        {
            con.Open();
            SqlDataAdapter a = new SqlDataAdapter("SELECT Eaten_food.Cardserial , Eaten_food.Date , Eaten_food.Turn , Avb_food_count , Reserve_count from Reserve inner join Eaten_food on Reserve.Cardserial = Eaten_food.Cardserial group by Eaten_food.Date", con);
            SqlCommandBuilder comdBuilder = new SqlCommandBuilder(a);
            DataTable t = new DataTable();
            //t.Locale = System.Globalization.CultureInfo.InvariantCulture;
            a.Fill(t);
            bindingSource3.DataSource = t;

            /// bind the grid view with binding source
           Reserve_dataGridView.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.AllCellsExceptHeader);
            Reserve_dataGridView.ReadOnly = true;
            Reserve_dataGridView.DataSource = bindingSource3;

            Reserve_dataGridView.DataSource = t;
            con.Close();
        }
    }

我该如何解决？

Answer 1

问题出在你的sql查询上。如果您使用 Group By，则无法选择未分组或未聚合的列(例如，使用 Min/Max/Avg/Count)。

因此您可以通过这种方式使其工作，例如，在此处更改您的旧查询:

SELECT eaten_food.cardserial, 
       eaten_food.date, 
       eaten_food.turn, 
       avb_food_count, 
       reserve_count 
FROM   reserve 
       INNER JOIN eaten_food 
               ON reserve.cardserial = eaten_food.cardserial 
GROUP  BY eaten_food.date 

到:

SELECT MIN(eaten_food.cardserial)AS Cardserial, 
       eaten_food.date, 
       MIN(eaten_food.turn) AS Turn, 
       SUM(avb_food_count) AS SumFoodCount, 
       SUM(reserve_count) AS SumReserveCount 
FROM   reserve 
       INNER JOIN eaten_food 
               ON reserve.cardserial = eaten_food.cardserial 
GROUP  BY eaten_food.date