标签：des blog http color 使用 os strong re
1、简单查询：
SQL：
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SELECT * FROM [Clients] WHERE Type=1 AND Deleted=0 ORDER BY ID |
EF：
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//Func形式 var clients = ctx.Clients.Where(c => c.Type == 1 && c.Deleted == 0) .OrderBy(c => c.ID) .ToList(); //Linq形式 var clients = from c in ctx.Clients where c.Type == 1 && c.Deleted==0 orderby c.ID select c; |
2、查询部分字段：
SQL：
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SELECT ID,Name FROM [Clients] WHERE Status=1 |
EF：
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//Func形式 var clients = ctx.Clients.Where(c => c.Status == 1) .Select(c => new { c.ID, Name = c.ComputerName }) .ToList(); //Linq形式 var clients = from c in ctx.Clients where c.Status == 1 select new { c.ID, Name = c.ComputerName }; ： |
3、查询单一记录：
SQL:
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SELECT * FROM [Clients] WHERE ID=100 |
EF：
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//Func形式 var client = ctx.Clients.FirstOrDefault(c => c.ID == 100); //Linq形式 var client = (from c in ctx.Clients where c.ID = 100 select c).FirstOrDefault(); |
4、LEFT JOIN 连接查询
SQL：
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SELECT c.ID , c.ComputerName , g.Name GroupNameFROM [Clients] c LEFT JOIN [Groups] g ON c.GroupID = g.IDWHERE c.Status = 1 |
EF：
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//Func形式 var clients = ctx.Clients.Where(c => c.Status == 1) .Select(c => new { c.ID, c.ComputerName, GroupName = ctx.Groups.FirstOrDefault(g => g.ID == c.GroupID).Name }) .ToList(); //Linq形式 var clients = from c in ctx.Clients where c.Status == 1 select new { c.ID, c.ComputerName, GroupName = (from g in ctx.Groups where g.ID == c.GroupID select g.Name).FirstOrDefault() }; |
5、INNER JOIN 连接查询：
SQL：
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SELECT c.ID , c.ComputerName , g.Name GroupNameFROM [Clients] c INNER JOIN [Groups] g ON c.GroupID = g.IDWHERE c.Status = 1ORDER BY g.Name |
EF：
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//Func形式 var clients = ctx.Clients.Where(c => c.Status == 1) .Join(ctx.Group, c => c.GroupID, g => g.ID, (c,g) => { c.ID, c.ComputerName, GroupName = g.Name }) .OrderBy(item => item.GroupName) .ToList(); //Linq形式1 var clients = from c in ctx.Clients from g in ctx.Groups where c.GroupID == g.ID orderby g.Name select new { c.ID, c.ComputerName, GroupName = g.Name }; //Linq形式2 var clients = from c in ctx.Clients where c.Status == 1 join g in ctx.Group on c.GroupID equals g.ID into result from r in result order by r.Name select new { c.ID, c.ComputerName, GroupName = r.Name }; |
6、分页
SQL：
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-- 方案1 SELECT TOP 10 *FROM [Clients]WHERE Status = 1 AND ID NOT IN ( SELECT TOP 20 ID FROM [Clients] WHERE Status = 1 ORDER BY ComputerName )ORDER BY ComputerName --方案2 SELECT *FROM ( SELECT * , ROW_NUMBER() OVER ( ORDER BY ComputerName ) AS RowNo FROM [Clients] WHERE Status = 1 ) tWHERE RowNo >= 20 AND RowNo < 30 |
EF：
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//Func形式 var clients = ctx.Clients.Where(c => c.Status=1) .OrderBy(c => c.ComputerName) .Skip(20) .Take(10) .ToList(); //Linq形式 var clients = (from c in ctx.Clients orderby c.ComputerName select c).Skip(20).Take(10); |
7、分组统计：
SQL：
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SELECT Status , COUNT(*) AS CntFROM [Clients]GROUP BY StatusORDER BY COUNT(*) DESC |
EF：
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//Func形式 var result = ctx.Clients.GroupBy(c => c.Status) .Select(s => new { Status = s.Key, Cnt = s.Count() }) .OrderByDescending(r => r.Cnt); //Linq形式 var result = from c in ctx.Clients group c by c.Status into r orderby r.Count() descending select new { Status = r.Key, Cnt = r.Count() }; |
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标签：des blog http color 使用 os strong re
原文地址：http://www.cnblogs.com/wangky/p/3868262.html
