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Eager load polymorphic
...able alone, since multiple tables represent the other end of the join, and SQL, as far as I know, does not allow you join a table named by the value stored in a column. By defining the extra relationship belongs_to :shop, you are giving ActiveRecord the information it needs to complete the join.
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Use email address as primary key?
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@onedaywhen: Yep! Otherwise why would SQL support cascading updates?
– Bill Karwin
Sep 27 '10 at 17:52
18
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How to sort objects by multiple keys in Python?
...der.
This means that the equivalent of ORDER BY name ASC, age DESC (using SQL notation) for a list of dictionaries can be done like this:
items.sort(key=operator.itemgetter('age'), reverse=True)
items.sort(key=operator.itemgetter('name'))
Note how the items are first sorted by the "lesser" attri...
How to implement a many-to-many relationship in PostgreSQL?
...itle is self-explanatory. How do you create the table structure in PostgreSQL to make a many-to-many relationship.
1 Answe...
What's the best way to join on the same table twice?
...o corresponding exists on the right. For me this works in Microsoft Access SQL (they require the parenthesis!)
SELECT t.PhoneNumber1, t.PhoneNumber2, t.PhoneNumber3
t1.SomeOtherFieldForPhone1, t2.someOtherFieldForPhone2, t3.someOtherFieldForPhone3
FROM
(
(
Table1 AS t LEFT JOIN Table2 AS t3 ...
程序员必知 —— 编程语言创始人 - 创意 - 清泛网 - 专注C/C++及内核技术
...发在Unix上运行的Emacs类编辑器Gosling Emacs（以C语言编写，使用Mocklisp作为扩展语言）。1983年获得了美国卡内基梅隆大学计算机科学博士学位，博士论文的题目是："The Algebraic Manipulation of Constraints"。毕业后到IBM工作，设计IBM第一代...
10 条真心有趣的 Linux 命令 - 创意 - 清泛网 - 专注C/C++及内核技术
...f unixmen
#figlet -f block.flf unixmen
当然，你也可以尝试使用其他的选项。
5.asciiquarium
这个命令会将你的终端变成一个海洋馆。
下载term animator：
# wget http://search.cpan.org/CPAN/authors/id/K/KB/KBAUCOM/Term-Animation-2.4.tar.gz
安装并且配...
vector删除元素erase和通用算法remove区别 - C/C++ - 清泛网 - 专注C/C++及内核技术
...ctor的begin和end仍旧会得到原来序列的大小范围的。
MARK：使用erase和remove函数都要注意删除元素时必须注意是否需要释放内存。如果vector存放的是指向动态创建对象的指针，那么必须确保指向的对象能够释放。
vector erase remove 区...
解决：Run-Time Check Failure #0，The value of ESP was not properly sav...
...的是VC++，那么直接用第一种定义就ok了。
注意，上面是使用 MFC （DLL）的做法。
如果是WIN32 DLL，得相应的去掉WINAPI ，__stdcall ，FAR PASCAL 这几个参数。因为WIN32 DLL 默认的入栈方式为 __cedcall方式，不是__stdcall方式。
具体的组合...