转:http://www.cnblogs.com/knowledgesea/p/3897665.html

1.简单linq查询

//1var ss = from r in db.Am_recProSchemeselect r;//2var ss1 = db.Am_recProScheme;//3string sssql = "select * from Am_recProScheme";

2.带where的查询

//1var ss = from r in db.Am_recProSchemewhere r.rpId > 10select r;//2var ss1 = db.Am_recProScheme.Where(p => p.rpId > 10);//3string sssql = "select * from Am_recProScheme where rpid>10";

3.简单的函数计算(Count,min,max,sum)

//1////获取最大的rpId//var ss = (from r in db.Am_recProScheme//          select r).Max(p => p.rpId);////获取最小的rpId//var ss = (from r in db.Am_recProScheme//          select r).Min(p => p.rpId);//获取结果集的总数//var ss = (from r in db.Am_recProScheme                  //         select r).Count();//获取rpId的和var ss = (from r in db.Am_recProSchemeselect r).Sum(p => p.rpId);//2//var ss1 = db.Am_recProScheme.Max(p=>p.rpId);//var ss1 = db.Am_recProScheme.Min(p => p.rpId);//var ss1 = db.Am_recProScheme.Count() ;var ss1 = db.Am_recProScheme.Sum(p => p.rpId);Response.Write(ss);//3string sssql = "select max(rpId) from Am_recProScheme";sssql = "select min(rpId) from Am_recProScheme";sssql = "select count(1) from Am_recProScheme";sssql = "select sum(rpId) from Am_recProScheme";

4.排序  order by desc/asc

var ss = from r in db.Am_recProSchemewhere r.rpId > 10orderby r.rpId descending  //倒序//  orderby r.rpId ascending   //正序select r;//正序var ss1 = db.Am_recProScheme.OrderBy(p => p.rpId).Where(p => p.rpId > 10).ToList();//倒序var ss2 = db.Am_recProScheme.OrderByDescending(p => p.rpId).Where(p => p.rpId > 10).ToList();string sssql = "select * from Am_recProScheme where rpid>10 order by rpId [desc|asc]";

5.top(1)

//如果取最后一个可以按倒叙排列再取值var ss = (from r in db.Am_recProScheme                     select r).FirstOrDefault();//()linq to ef 好像不支持 Last() var ss1 = db.Am_recProScheme.FirstOrDefault();//var ss1 = db.Am_recProScheme.First();          string sssql = "select top(1) * from Am_recProScheme";

6.跳过前面多少条数据取余下的数据

//1var ss = (from r in db.Am_recProSchemeorderby r.rpId descendingselect r).Skip(10); //跳过前10条数据,取10条之后的所有数据   //2  var ss1 = db.Am_recProScheme.OrderByDescending(p => p.rpId).Skip(10).ToList();//3string sssql = "select * from  (select ROW_NUMBER()over(order by rpId desc) as rowNum, * from [Am_recProScheme]) as t where rowNum>10";

7.分页数据查询

//1var ss = (from r in db.Am_recProSchemewhere r.rpId > 10orderby r.rpId descendingselect r).Skip(10).Take(10); //取第11条到第20条数据                   //2 Take(10): 数据从开始获取,获取指定数量(10)的连续数据var ss1 = db.Am_recProScheme.OrderByDescending(p => p.rpId).Where(p => p.rpId > 10).Skip(10).Take(10).ToList();//3string sssql = "select * from  (select ROW_NUMBER()over(order by rpId desc) as rowNum, * from [Am_recProScheme]) as t where rowNum>10 and rowNum<=20";

8.包含,类似like'%%'

//1var ss = from r in db.Am_recProSchemewhere r.SortsText.Contains("张")select r;//2var ss1 = db.Am_recProScheme.Where(p => p.SortsText.Contains("张")).ToList();//3string sssql = "select * from Am_recProScheme where SortsText like '%张%'";

9.分组group by

//1var ss = from r in db.Am_recProSchemeorderby r.rpId descendinggroup r by r.recType into nselect new{n.Key,  //这个Key是recTyperpId = n.Sum(r => r.rpId), //组内rpId之和MaxRpId = n.Max(r => r.rpId),//组内最大rpIdMinRpId = n.Min(r => r.rpId), //组内最小rpId
                     };foreach (var t in ss){Response.Write(t.Key + "--" + t.rpId + "--" + t.MaxRpId + "--" + t.MinRpId);}//2var ss1 = from r in db.Am_recProSchemeorderby r.rpId descendinggroup r by r.recType into nselect n;foreach (var t in ss1){Response.Write(t.Key + "--" + t.Min(p => p.rpId));}//3var ss2 = db.Am_recProScheme.GroupBy(p => p.recType);foreach (var t in ss2){Response.Write(t.Key + "--" + t.Min(p => p.rpId));}//4string sssql = "select recType,min(rpId),max(rpId),sum(rpId) from Am_recProScheme group by recType";

10.连接查询

//1var ss = from r in db.Am_recProSchemejoin w in db.Am_Test_Result on r.rpId equals w.rsIdorderby r.rpId descendingselect r;//2var ss1 = db.Am_recProScheme.Join(db.Am_Test_Result, p => p.rpId, r => r.rsId, (p, r) => p).OrderByDescending(p => p.rpId).ToList();//3string sssql = "select r.* from  [Am_recProScheme] as r inner join [dbo].[Am_Test_Result] as t on r.[rpId] = t.[rsId] order by r.[rpId] desc";

11.sql中的in

//1var ss = from p in db.Am_recProSchemewhere (new int?[] { 24, 25,26 }).Contains(p.rpId)select p;foreach (var p in ss){Response.Write(p.Sorts);}//2string st = "select * from Am_recProScheme where rpId in(24,25,26)";

转载于:https://www.cnblogs.com/herizai/p/7026517.html

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