大约有 9,000 项符合查询结果（耗时：0.0426秒） [XML]
Chaining multiple filter() in Django, is this a bug?
...
As you can see in the generated SQL statements the difference is not the "OR" as some may suspect. It is how the WHERE and JOIN is placed.
Example1 (same joined table) :
(example from https://docs.djangoproject.com/en/dev/topics/db/queries/#spanning-mult...
Good example of livelock?
...ple is two competing processes live locking in an attempt to correct for a SQL server deadlock, with each process using the same wait-retry algorithm for retrying. While it's the luck of timing, I have seen this happen on separate machines with similar performance characteristics in response to a me...
炒股是世界难题！历史上那些名人炒股水平 - 轻松一刻 - 清泛网 - 专注C/C++...
...号码，便于人们识别。蒋介石当时的代号是“蒋伟记”，使用的牌号为“恒泰号”，他还是这个牌号下的股东。当时他以极小的4股“恒泰号”进入股市。通过炒作一年内使股价由30元涨至120元，收益翻了四倍；第二年又涨到200元...
Advantage of creating a generic repository vs. specific repository for each object?
...aces, but a base class for the implementations. For example, using LINQ to SQL, you could do:
public abstract class Repository<TEntity>
{
private DataContext _dataContext;
protected Repository(DataContext dataContext)
{
_dataContext = dataContext;
}
protected IQu...
2016电商“死亡”名单（上半年） - 资讯 - 清泛网 - 专注IT技能提升
...进行了反思：A轮融资后开始盲目扩张，大幅增员，大量使用猎头招聘所谓的行业“大牛”、顶尖技术人才，盲目相信某某大公司背景、相信所谓专业性人才和经验，盲目制定战略，在毫无供应链经验的时候，涉足供应链，大量...
Django: “projects” vs “apps”
...en contains a few other things, including but not limited to wsgi scripts, sql scripts etc.
django's management extensions rely on subdirectories. So it makes sense to name packages appropriately.
In short, the reason there is a convention is the same as any other convention - it helps when it com...
MySQL: @variable vs. variable. What's the difference?
...
MySQL has a concept of user-defined variables.
They are loosely typed variables that may be initialized somewhere in a session and keep their value until the session ends.
They are prepended with an @ sign, like this: @var
You ...
MVC Razor view nested foreach's model
...w it does its work is important here.
(Note other frameworks like LINQ to SQL do similar things by walking an expression tree and building a different grammar, that this case a SQL query)
How does the Model Binder work?
So once you get that, we have to briefly talk about the model binder. When th...
How to append rows to an R data frame
...operation and couple it with manually doubling the table when needed.
Use RSQLite and append to the table held in memory.
data.frame's own ability to grow and use custom environment (which has reference semantics) to store the data.frame so it will not be copied on return.
Here is a test of all th...
开源邮件传输代理软件 -- Postfix 介绍 - 开源 & Github - 清泛网 - 专注C/C++及内核技术
...投递代理procmail。在流行的linux发行版本RedHat中，我们就使用procmail作为最终的本地投递代理。
远程投递代理SMTP进程根据收件人地址查询一个SMTP服务器列表，按照顺序连接每一个SMTP服务器，根据性能对该表进行排序。在系统负...