一步一步学Linq to sql(四):查询句法

前言

  本次主要来学习并记录一下Linq基本的查询语法。

In 操作

 查询指定城市中的客户

var in操作 = from c in ctx.Customers
 
                    where new string[] { "Brandenburg", "Cowes", "Stavern" }.Contains(c.City)
 
                    select c;

对应SQL语句

select * from Customers where City in('Brandenburg', 'Cowes', 'Stavern')

查询结果

  

Join 操作

 内连接只能查询出已有分类的物品列表

var innerjoin = from p in ctx.Products 

                        join c in ctx.Categories 

                        on p.CategoryID equals c.CategoryID
 
                        select p.ProductName;

对应SQL语句

  

SELECT [t0].ProductName
 
FROM [dbo].[Products] AS [t0]
 
INNER JOIN [dbo].[Categories] AS [t1] ON [t0].[CategoryID] = ([t1].[CategoryID])

查询结果为

 

distinct

查询顾客覆盖的国家

var 过滤相同项 = (from c in ctx.Customers orderby c.Country select c.Country).Distinct(); 

相应的SQL语句

SELECT DISTINCT [t0].[Country]
 
FROM [dbo].[Customers] AS [t0]

 

 

posted @ 2013-04-13 23:07 aehyok 阅读(...) 评论(...) 编辑 收藏