如何使用c#从两个以上的MS Access数据库表中检索数据

Posted 2023-05-07

【中文标题】如何使用c#从两个以上的MS Access数据库表中检索数据

【英文标题】：How to retrieve data from more then two table of MS Access database using c#

【发布时间】：2014-04-13 07:30:52

【问题描述】：

我想从 3 个相互连接的表中检索 MS Access 数据库中的数据。 我在业务层写了这段代码

public List<ProductOrderModel> Show()

         OleDbConnection cn;
         try
         
             ProductOrderModel dtoobj = new ProductOrderModel();
             DataLayer dalobj = new DataLayer();
             OleDbCommand cmdshow = new OleDbCommand();

             cmdshow.CommandText = "select [CustomerVT].[Customer_Name],[OrderVT].[Order_Date],[ProductVT].[Price],[ProductVT].[Item_Name],[OrderVT].[Quantity],[OrderVT].[Order_ID] from  [OrderVT] inner join [CustomerVT] on [OrderVT].[Customer_ID]=[CustomerVT].[Customer_ID] inner join [ProductVT] on [OrderVT].[Product_ID]=[ProductVT].[Product_ID] ";

              List<ProductOrderModel> Ldemo = new List<ProductOrderModel>();

             return dalobj.executereader(Ldemo, cmdshow, "BillingData");
   
   catch (Exception ex2)
   
       throw new DataException("error....." + ex2.Message);
   

ExecuteReader() 的代码是..

public List<ProductOrderModel> executereader(List<ProductOrderModel> Ldemo, OleDbCommand cmdshow, string tablename)

        OleDbConnection cn;

        try
        
            cn = this.getconnection();

            cmdshow.Connection = cn;
            cn.Open();

            OleDbDataReader rd = cmdshow.ExecuteReader();

            while (rd.Read())
            
                ProductOrderModel dtoobj1 = new ProductOrderModel();

                dtoobj1.InvoiceNo = Convert.ToInt32(rd["Order_ID"].ToString());
                dtoobj1.CustomerName = rd["Customer_Name"].ToString();

                dtoobj1.ItemName = rd["Item_Name"].ToString();
                dtoobj1.Quantity = Convert.ToInt32(rd["Quantity"].ToString());
                dtoobj1.Price = Convert.ToInt32(rd["Price"].ToString());
                dtoobj1.OrderDate = Convert.ToDateTime(rd["Order_Date"].ToString());
                Ldemo.Add(dtoobj1);
            

            cn.Close();
            return Ldemo;
        
        catch (Exception ex2)
        
            throw new DataException("error....." + ex2.Message);
        

但它显示错误

查询表达式“[OrderVT].[Customer_ID]=[CustomerVT].[Customer_ID] 内部联接 [ProductVT] on [OrderVT].[Product_ID]=[ProductVT].[Product_ID]”中存在语法错误（缺少运算符）

请帮忙。提前致谢。

【参考方案1】：

像下面这样使用括号

select [CustomerVT].[Customer_Name],[OrderVT].[Order_Date],[ProductVT].[Price],[ProductVT].[Item_Name],[OrderVT].[Quantity],[OrderVT].[Order_ID] 
from  ([OrderVT] 
inner join [CustomerVT] on [OrderVT].[Customer_ID]=[CustomerVT].[Customer_ID])
inner join [ProductVT] on [OrderVT].[Product_ID]=[ProductVT].[Product_ID]