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MongoDB仿关系型数据库Group聚合例子 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...系型数据库例子，通过BsonJavaScript脚本实现。相当的SQL：select * from GroupDemo a right join (select userName,max(date) maxdate from GroupDemo group by userName) b on a date=b maxdate
namespace MongoGroupDemo
{
class Program
{
private static string MongoConnStr...
闲扯Nginx的accept_mutex配置 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...相关的解释：
OS may wake all processes waiting on accept() and select(), this is called thundering herd problem. This is a problem if you have a lot of workers as in Apache (hundreds and more), but this insensible if you have just several workers as nginx usually has. Therefore turning acc...
领域驱动设计系列（五）:事件驱动之异步事件 - 更多技术 - 清泛网 - 专注C/...
... var handlers = _eventHandlerFactory.GetHandlers<T>();
handlers.Select(h => Task.Factory.StartNew(() => HandleEvent<T>(h, @event)));
}
这段代码执行完，尽然发现Handler没有执行，好吧，原因是IQueryable的延迟执行，所以我们需要调用一下ToL...
date(): It is not safe to rely on the system\'s timezone settings.解决...
...tting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone.(2)
It is not safe to rely on the system解决方法,其实就是时区设置不正确造成的,本文提供了3种方法来解决...
Linq 多字段排序，二次排序 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...ed = source.OrderByDescending( t => t.f1 ).ThenBy( t => t.f2 );类似SQL：select * from t1 order by f1 d...Linq：ordered = source.OrderByDescending( t => t.f1 ).ThenBy( t => t.f2 );
类似SQL：select * from t1 order by f1 desc ,f2 asc
这种写法里 OrderBy、ThenBy 是升序的，OrderByD...
C#泛型(List)中基类和子类 怎么转换？ - 更多技术 - 清泛网 - 专注C/C++及内核技术
...函数Foo，Foo支持所有子类列表。
方法一：
Foo(childList.Select(p => p as BaseClass).ToList())
上述 Select 转换是双向的，基类转子类也没问题。
方法二：
List<BaseClass> baseList = new List<BaseClass>();
baseList.AddRange(childList);
Foo(baseList);
...
虚拟机安装CentOS出错：EDD:Error 8000 reading sector 2106934 - 更多技术...
...
Getting closer!
When i start to install every thing seem to be fine.
1.Select language k
2.select location k
3.configure keyboard k
4.network config k
then it gets stuck on a purple screen with nothing in it and a white/black bottom that it lets me type in but nothing else happens.
http:/...
C#泛型(List)中基类和子类 怎么转换？ - .NET(C#) - 清泛IT论坛，有思想、有深度
...函数Foo，Foo支持所有子类列表。
方法一：
Foo(childList.Select(p => p as BaseClass).ToList())
上述 Select 转换是双向的，基类转子类也没问题。
方法二：
List<BaseClass> baseList = new List<BaseClass>();
baseList.AddRange(childList);
Foo(b...
虚拟机安装CentOS出错：EDD:Error 8000 reading sector 2106934 - 环境配置...
...
Getting closer!
When i start to install every thing seem to be fine.
1.Select language k
2.select location k
3.configure keyboard k
4.network config k
then it gets stuck on a purple screen with nothing in it and a white/black bottom that it lets me type in but nothing else happens.
http:/...
App Inventor 2 如何连接MySQL数据库（阿里云数据库） · App Inventor 2 中文网
...接信息
测试代码
注意事项：
返回 HTTP 代码 200 表示SELECT 查询成功
返回 HTTP 代码 201 表示不是有效的 SELECT 查询
返回 HTTP 代码 400，表示 SQL 查询错误
请注意SQL注入风险，加强php代码的检查逻辑
前端代码块
执行sql语...