var 构建匿名类型1 = from c in ctx.GetTable<Customers>()
select new
{
城市 = c.City,
名字 = c.Name
};
var 构建匿名类型2 = from emp in ctx.GetTable<Customers>()
select new
{
城市 = emp.City,
名字 = emp.Name
};
var 多条件 = from c in ctx.GetTable<Customers>()
where c.Name == "Jay" && c.City == "雷州"
select new
{
名字 = c.City,
城市 = c.City
};
var 排序 = from c in ctx.GetTable<Customers>()
where c.City == "雷州"
orderby c.Name descending, c.City ascending
select new
{
名字 = c.Name,
城市 = c.City
};
//按照每页 10 条记录，查询第二页的顾客
var 分页 = (from c in ctx.GetTable<Customers>() select c).Skip(10).Take(10);
//根据顾客的国家分组，查询顾客数大于 5 的国家名和顾客数
var 一般分组 = from c in ctx.GetTable<Customers>()
group c by c.City into g
where g.Count() > 5
orderby g.Count() descending
select new
{
国家=g.Key,
顾客数=g.Count()
};
//根据国家和城市分组，查询顾客覆盖的国家和城市
var 匿名类型分组 = from c in ctx.GetTable<Customers>()
group c by new { c.City, c.Name } into g
orderby g.Key.City, g.Key.Name
select new
{
国家 = g.Key.Name,
城市 = g.Key.City
};
var 过滤相同项 = (from c in ctx.GetTable<Customers>() orderby c.Name select c.Name).Distinct();
var 连接并且过滤相同项 = (from c in ctx.GetTable<Customers>()
where c.City.Contains("A")
select c)
.Union(from c in ctx.GetTable<Customers>()
where c.Name.StartsWith("A")
select c).OrderBy(c => c.City);
var 连接并且不过滤相同项 = (from c in ctx.GetTable<Customers>()
where c.City.Contains("A")
select c).Concat
(from c in ctx.GetTable<Customers>() where c.City.StartsWith("A") select c)
.OrderBy(c => c.City);
//查询城市是 A 打头的顾客和城市包含 A 的顾客的交集，并按照顾客名字排序
var 取相交项 = (from c in ctx.GetTable<Customers>()
where c.City.Contains("A")
select c).Intersect
(from c in ctx.GetTable<Customers>()
where c.City.StartsWith("A")
select c).OrderBy(c => c.City);
//查询城市包含 A 的顾客并从中删除城市以 A 开头的顾客，并按照顾客名字排序
var 排除相交项 = (from c in ctx.GetTable<Customers>()
where c.City.StartsWith("A")
select c).Except
(from c in ctx.GetTable<Customers>()
where c.Name.StartsWith("A")
select c).OrderBy(c => c.Name);
//查询订单数超过 5 的顾客信息
var 子查询 = from c in ctx.GetTable<Customers>()
where
(from o in ctx.GetTable<Customers>()
group o by o.CustomerID into o
where
o.Count() > 5
select o.Key).Contains(c.CustomerID)
select c;
//查询指定城市中的客户
var in操作 = from c in ctx.GetTable<Customers>()
where new string[] { "B", "A", "C" }.Contains(c.City)
select c;
//内连接，没有分类的产品查询不到
var innerjoin = from p in ctx.GetTable<Customers>()
join c in ctx.GetTable<Customers>()
on p.CustomerID equals c.CustomerID
select p.Name;
//外连接，没有分类的产品也能查询到
var leftjoin = from p in ctx.GetTable<Customers>()
join c in ctx.GetTable<Customers>()
on p.City equals c.City
into pro
from x in pro.DefaultIfEmpty()
select p.Name;
var 单结果集存储过程 =
from c in ctx.sp_singleresultset()
where c.Name.StartsWith("A")
select c;
var 多结果集存储过程 = ctx.sp_multiresultset();
var Customer = 多结果集存储过程.GetResult<Customers>();
var Employees = 多结果集存储过程.GetResult<Employee>();