knrt.net
当前位置:首页 >> linq to sql join >>

linq to sql join

可以用 into 语法,配合 DefaultIfEmpty() 方法加载右侧表中的空值。例子:var query =from r in db.Rolesjoin sr in(from ss in db.StaffInRoleswhere ss.StaffId == staffIdselect ss)on r.Id equals sr.RoleIdinto xfrom y in x.DefaultIfEmp...

var q= from n in db.NewsModel join b in db.BigClassModel on n.BigClassID equals b.BigClassID join s in db.SmallClassModel on n.SmallClassID equals s.SmallClassID orderby n.AddTime descending select new { n.NewsID, n.BigClassID,...

}; 注意这里最后可以通过 y != null 来判断右值是否为空。 这个Linq to sql 语句生成的对应 SQL 为:exec sp_executesql N'SELECT [t0].[Id] AS [RoleId], [t0].[Name] AS [RoleName], (CASEWHEN [t2].[test] IS NOT NULL THEN 1ELSE 0END) AS [...

var q= from n in db.NewsModel join b in db.BigClassModel on n.BigClassID equals b.BigClassID join s in db.SmallClassModel on n.SmallClassID equals s.SmallClassID orderby n.AddTime descending select new { n.NewsID, n.BigClassID,...

可以用 into 语法,配合 DefaultIfEmpty() 方法加载右侧表中的空值。 例子:var query = from r in db.Rolesjoin sr in(from ss in db.StaffInRoles where ss.StaffId == staffIdselect ss)on r.Id equals sr.RoleIdinto xfrom y in x.DefaultIf...

分少点!回头入我团队帮我打工偿还呀!O(∩_∩)O哈哈~ --------- 你根本不是级联的问题,而是要保持Contains方法功能的特殊性,它有模糊匹配的功能! ------ 第一种方式:轻装上阵,小集合拼合! var names = dataLst.Select(item => item.Name).S...

左连接left outer join,除了满足连接条件的行,还包括左表的所有行。 右连接right outer join,除了满足连接条件的行,还包括右表的所有行。 eg:var q = from e in db.Employees join o in db.Orders on e equals o.Employee into ords select...

你是指多个查询条件么? from n in DBContext.TableA where n.A1== a && n.A2== b select n

from A in DFZFORMT055 join B in FM_CODE_LIST on A.MoneyType = B.ITEM_VALUE AND B.FORM_KIND = 'DFZ.FORM.T055' AND B.FIELD_NAME= 'MoneyType' join C in JOIN FM_CODE_LIST on A.PayMentType = C.ITEM_VALUE AND C.FORM_KIND = 'DFZ.FORM....

这两种都是直接查询数据库的,没有在内存中存储, 但要是这样两种都可以先把数据缓存到内存中再查: List ba=Db.BlogArt.toList(); ba.where(a => a.BlogCata_ID== 1) var ls= from a in Db.BlogArt.toList() where a.BlogCata_ID==1 select a;

网站首页 | 网站地图
All rights reserved Powered by www.knrt.net
copyright ©right 2010-2021。
内容来自网络,如有侵犯请联系客服。zhit325@qq.com