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  • 基础性的linq&Lambda语句

      1.左右链接

        //此处相当于left join 左连接查询 左右链接替换主从就行了 

        var query = db.CRM_BIGDATA.GroupJoin(db.CRM_BIGDATA_EMAIL_REF, (CRM_BIGDATA x) => x.RID, (CRM_BIGDATA_EMAIL_REF y)=>Convert.ToInt32(y.BIG_DATA_ID), (x, list) => new { x, list });

               //左连接

        var resultLeft = from s in db.CRM_BIGDATA

               join x in db.CRM_BIGDATA_EMAIL_REF
               on s.RID equals Convert.ToInt32(x.BIG_DATA_ID) into empy
               from x in empy.DefaultIfEmpty()
               select new { s, x };

        

        //右链接
        var resultReight = from s in db.CRM_BIGDATA_EMAIL_REF
                  join x in db.CRM_BIGDATA
                  on s.RID equals Convert.ToInt32(x.BIGDATAID) into empy
                 from x in empy.DefaultIfEmpty()
                  select new { s, x };

          2.分组查询

         var queryLambdaGroup = db.CRM_BIGDATA.GroupBy(x => x.KEYWORD).ToList();

         var queryLinqGroup = from u in db.CRM_BIGDATA group u by u.KEYWORD into g select g;

          3.升降序

        //将序 升序排法

         var quLamOrder = db.CRM_BIGDATA.GroupBy(s=>s.KEYWORD).OrderBy(x => x.Key).OrderByDescending(y=>y.Key).ToList();

         var quLinqOrder = from u in db.CRM_BIGDATA group u by u.KEYWORD into g orderby g.Key descending select g;

          4.内链接查询

         var quLamJoin = db.CRM_BIGDATA.Join(db.CRM_BIGDATA_EMAIL_REF, (CRM_BIGDATA x) => x.RID, (CRM_BIGDATA_EMAIL_REF y) => Convert.ToInt32(y.BIG_DATA_ID), (x, y) => new { x, y });

       5.let 用法

            var quLinqLet = from u in db.CRM_BIGDATA let length = u.KEYWORD.Length select new { len = length, u };

           6.介绍工具

        <1>LinqPad: 官方下载: http://www.linqpad.net/    

               具体用法:http://www.cnblogs.com/AlexLiu/archive/2008/10/24/1318998.html

               使用说明: 可以生成其LINQ查询对应的lambda和SQL语句

        <2>Linqer :   官方下载:http://www.sqltolinq.com/

               具体用法:http://www.cnblogs.com/huangxincheng/archive/2011/05/12/2044990.html

               使用说明: SQL语句转Linq

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  • 原文地址:https://www.cnblogs.com/RainbowFife/p/6472897.html
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