Linq 基本語法
阿新 • • 發佈:2018-11-03
以下都是轉載內容
1.簡單的linq語法
//1
var ss = from r in db.Am_recProScheme
select r;
//2
var ss1 = db.Am_recProScheme;
//3
string sssql = "select * from Am_recProScheme";
2.帶where的查詢
//1 var ss = from r in db.Am_recProScheme where r.rpId > 10 select r; //2 var ss1 = db.Am_recProScheme.Where(p => p.rpId > 10); //3 string sssql = "select * from Am_recProScheme where rpid>10";
3.簡單的函式計算(count,min,max,sum)
//1 ////獲取最大的rpId //var ss = (from r in db.Am_recProScheme // select r).Max(p => p.rpId); ////獲取最小的rpId //var ss = (from r in db.Am_recProScheme // select r).Min(p => p.rpId); //獲取結果集的總數 //var ss = (from r in db.Am_recProScheme // select r).Count(); //獲取rpId的和 var ss = (from r in db.Am_recProScheme select 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); //3 string 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_recProScheme where r.rpId > 10 orderby 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)
//如果取最後一個可以按倒敘排列再取值
var ss = (from r in db.Am_recProScheme
select r).FirstOrDefault();
//()linq to ef 好像不支援 Last()
var ss1 = db.Am_recProScheme.FirstOrDefault();
//var ss1 = db.Am_recProScheme.First();
string sssql = "select top(1) * from Am_recProScheme";
6.跳過前面多少條資料取餘下的資料
//1
var ss = (from r in db.Am_recProScheme
orderby r.rpId descending
select r).Skip(10); //跳過前10條資料,取10條之後的所有資料
//2
var ss1 = db.Am_recProScheme.OrderByDescending(p => p.rpId).Skip(10).ToList();
//3
string sssql = "select * from (select ROW_NUMBER()over(order by rpId desc) as rowNum, * from [Am_recProScheme]) as t where rowNum>10";
7.分頁資料查詢
//1
var ss = (from r in db.Am_recProScheme
where r.rpId > 10
orderby r.rpId descending
select r).Skip(10).Take(10); //取第11條到第20條資料
//2 Take(10): 資料從開始獲取,獲取指定數量(10)的連續資料
var ss1 = db.Am_recProScheme.OrderByDescending(p => p.rpId).Where(p => p.rpId > 10).Skip(10).Take(10).ToList();
//3
string 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,類似like '%%'
//1
var ss = from r in db.Am_recProScheme
where r.SortsText.Contains("張")
select r;
//2
var ss1 = db.Am_recProScheme.Where(p => p.SortsText.Contains("張")).ToList();
//3
string sssql = "select * from Am_recProScheme where SortsText like '%張%'";
9.分組group by
//1
var ss = from r in db.Am_recProScheme
orderby r.rpId descending
group r by r.recType into n
select new
{
n.Key, //這個Key是recType
rpId = n.Sum(r => r.rpId), //組內rpId之和
MaxRpId = n.Max(r => r.rpId),//組內最大rpId
MinRpId = n.Min(r => r.rpId), //組內最小rpId
};
foreach (var t in ss)
{
Response.Write(t.Key + "--" + t.rpId + "--" + t.MaxRpId + "--" + t.MinRpId);
}
//2
var ss1 = from r in db.Am_recProScheme
orderby r.rpId descending
group r by r.recType into n
select n;
foreach (var t in ss1)
{
Response.Write(t.Key + "--" + t.Min(p => p.rpId));
}
//3
var ss2 = db.Am_recProScheme.GroupBy(p => p.recType);
foreach (var t in ss2)
{
Response.Write(t.Key + "--" + t.Min(p => p.rpId));
}
//4
string sssql = "select recType,min(rpId),max(rpId),sum(rpId) from Am_recProScheme group by recType";
10.連線查詢
//1
var ss = from r in db.Am_recProScheme
join w in db.Am_Test_Result on r.rpId equals w.rsId
orderby r.rpId descending
select r;
//2
var ss1 = db.Am_recProScheme.Join(db.Am_Test_Result, p => p.rpId, r => r.rsId, (p, r) => p).OrderByDescending(p => p.rpId).ToList();
//3
string 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
//1
var ss = from p in db.Am_recProScheme
where (new int?[] { 24, 25,26 }).Contains(p.rpId)
select p;
foreach (var p in ss)
{
Response.Write(p.Sorts);
}
//2
string st = "select * from Am_recProScheme where rpId in(24,25,26)";