Linq to SQL学习笔记——SELECT/WHERE语句

1.SELECT语句

    (1) 普通查询

         var list = from s in db.student select s.stuname;

    (2) 匿名类查询

         var list = from c in db.customer select new {name = c.firstname+" "+c.lastname};

    (3) 条件查询

         var list = from l in db.grade select new {name = l.name; level = l.score>60?"pass":"failed"};

    (4) 指定类型查询

         var list = from e in db.card select new Name {first = e.firstname;last=e.lastname};

    (5) 筛选查询

         var list = from s in db.student where s.id < 10 select s.name;

    (6) 匿名对象嵌套查询

         var list = from e in db.data select new {

                                                                   company = new { companyname = e.name;

                                                                                               companyphone = e.phone},

                                                                   manager = e.manager;

                                                                    }

    (7)  调用方法查询

         var list = from s in db.student select new {name=s.name,age=ageconvert(s.age)};

    (8) Distinct形式

         var list = (from s in db.student select s.name).distinct();

2. WHERE语句

    (1) 普通条件查询

          var list = from s in db.student where s.name = "Jack" select s;

    (2) 关系条件查询

         var list = from s in db.student where s.age>20 && s.sex ==1;

         var list = db.student.where(s=>s.age>20).where(s=>s.sex==1)

    (3) First形式（相当于SQL中Top(1)）

         student stu = db.student.first(s=>s.age>20);

本文出自 “咖啡色的梦” 博客