使用关联查询具有三个链接表的数据库

问题描述

我有一个数据库，其中有几个表使用关联链接。是否可以查询数据库以使用关联从表中提取记录？看下面的代码？



我试图从所有三个表中获取值，即从表BOOK提取P_C和STRIKE，从表OPTIONS提取OPT_MULTIPLIER和OPT_EXPIRY，最后从表SKEW提取SKEW_A 。



我可以获得一层下来的记录，但我不知道如何从两个表格中获取记录。这里http://imgur.com/D7kh1oE是映射图像的链接。



我尝试过：

I have a database with several tables linked using associations. Is it possible to query the database to extract records from tables two tiers down using the association? See code below?

I am trying to get values from all three tables i.e from table BOOK extract P_C and STRIKE, from table OPTIONS extract OPT_MULTIPLIER and OPT_EXPIRY, and finally from table SKEW extract SKEW_A.

I can get records one tier down, but I don't know how to get records from a table two tiers down. Here "http://imgur.com/D7kh1oE" is a link to the mapping image.

What I have tried:

using (lnkTRADERDataContext DATActx = new lnkTRADERDataContext())
{

    var qryBOOK = from B in DATActx.BOOKs where B.DEAL == 1
                  select new clsTRADER()
                  {
                      P_C = B.P_C,       //main table
                      STRIKE = B.STRIKE, //main table
                      OPT_EXP = B.OPTIONs.Single(X => X.OPT_EXPIRY),        //one tier down
                      OPT_MULT = B.OPTIONs.Single(X => X.OPT_MULTIPLIER),   //one tier down
                      SKEW_A = B.OPTIONs.SKEWs.Single(X => X.SKEW_A)        // two tiers down
               };
}

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