关系型数据之LinQ基本查询

如下图所示关系型数据,LinQ语句为:

var Query= from a in data.A

where a.admin==传入的用户名&&a.pwd==传入的密码(可以传入一个model实体)

join b in data.B

            on a.bid equals b.id into ab

            from r1 in ab.DefaultIfEmpty()

            join c in data.C

            on r1.cid equals c.id into bc

            from r2 in bc.DefaultIfEmpty()

            join d in data.D

            on r2.did equals d.id into cd

            from r3 in cd.DefaultIfEmpty()

select new

            {



//这里是table A 的id;

                  Id = a.Id,



//这里是table B的Name;

                  Name = r1.Name,

                  Pro = r2.Pro,

                  IpAdd = r3.IpAdd

            };



//转成数组形式;



        var list = Query.ToList();



//list[0].Name即表示整个LinQ查询的结果的第一条数据的table B的Name,以此类推;

 

注: r1可以.出table B的所有数据...以此类推;

r2==table C;

r3==table D;