'GROUP 附近的语法不正确，当它是不正确的语法时是什么意思？

Question

I am creating a form that I can add a menu item to display All Suppliers and Suppliers Quantity by Part number. So I got ReportSupplierDisplayALl to work when I ran. But When I try to run the form for the ReportSuppliersDisplayByPartnumber because When I enter the SupplierID and when I did it threw an exception. When it throws an exception, what does it mean by incorrect syntax?

    public DataTable DisplaySupplierByPartNumber(string PartNumber)
    {
        // Add using System.Data

        string queryString = "SELECT Suppliers.SupplierName, Suppliers.Email, Parts.PartName, SUM(Inventory.Quantity) AS SumOfQuantity, PartNumber " +
        "FROM ((Suppliers INNER JOIN Parts ON Suppliers.SupplierID = Parts.Supplier) INNER JOIN Inventory ON Parts.PartNumber = Inventory.PartNumber " +
        "INNER JOIN Employees ON Inventory.EmpID = Employees.EmpID " +
        "GROUP BY Suppliers.SupplierName, Suppliers.Email, Parts.PartName, Parts.PartNumber " +
        "HAVING Parts.PartNumber = @PartNumber " +
        "ORDER BY Suppliers.SupplierName ";

        using (SqlConnection con = new SqlConnection(_strCon))
        {
            try
            {
                SqlCommand command = new SqlCommand(queryString, con);
                command.Parameters.AddWithValue("@PartNumber", PartNumber );
                con.Open();
                SqlDataReader reader = command.ExecuteReader();
                DataTable theTable = new DataTable();
                theTable.Load(reader);
                return theTable;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

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Answer 1

Don't use "" For String use @ "Your Query And Make Sure You get all bracket correct" also change element take part number first then use your aggerate function

string queryString = @"SELECT S.SupplierName, S.Email, P.PartName, SUM(Inventory. Quantity) AS SumOfQuantity FROM Suppliers as s
INNER JOIN Parts as p on P.SupplierId=P.SupplierId
INNER JOIN Inventory ON Parts.PartNumber = Inventory.PartNumber 
INNER JOIN Employees ON Inventory.EmpID = Employees.EmpID 
GROUP BY S.SupplierName, S.Email, P.PartName, P.PartNumber 
HAVING Parts.PartNumber = @PartNumber
ORDER BY S.SupplierName"