Linq to SQL 内连接（inner join）与 左连接（left join）

 

左连接（两张表）

var list = from a in db.Specialty
                       join b in db.School on a.Specialty_School_id equals b.School_id into c
                       from d in c.DefaultIfEmpty()
                       select new { 
                            a.Specialty_id,
                            a.Specialty_name,
                            a.Specialty_mark,
                            a.Specialty_type,
                            a.Specialty_School_id,
                            d.School_id,
                            d.School_name,
                            d.School_mark,
                            d.School_address
                       };

 

 

 

内连接三张表

var list = from a in db.School
                       join b in db.Specialty on a.School_id equals b.Specialty_School_id 
                       join e in db.SchoolCalss on b.Specialty_id equals e.SchoolCalss_Specialty_id 
                       select new
                       {
                           b.Specialty_id,
                           b.Specialty_name,

                           a.School_id,
                           a.School_name,

                           e.SchoolCalss_id,
                           e.SchoolCalss_name,
                           e.SchoolCalss_mark,
                           e.SchoolCalss_Specialty_id
                       };