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Why use multiple columns as primary keys (composite primary key)
...nerated (non-intelligent) primary key, for example in this case OrderDetailId. But then you would not always see the relationship as easily. Some folks prefer one way; some prefer the other way.
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How to find Unused Amazon EC2 Security groups
... find a way to determine orphan security groups so I can clean up and get rid of them. Does anyone know of a way to discover unused security groups.
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How can I change an element's class with JavaScript?
...iques for changing classes
Modern browsers have added classList which provides methods to make it easier to manipulate classes without needing a library:
document.getElementById("MyElement").classList.add('MyClass');
document.getElementById("MyElement").classList.remove('MyClass');
if ( document...
Postgresql query between date ranges
... simpler if you use >= start AND < end.
For example:
SELECT
user_id
FROM
user_logs
WHERE
login_date >= '2014-02-01'
AND login_date < '2014-03-01'
In this case you still need to calculate the start date of the month you need, but that should be straight forward in any num...
Check/Uncheck checkbox with JavaScript (jQuery or vanilla)?
...
Javascript:
// Check
document.getElementById("checkbox").checked = true;
// Uncheck
document.getElementById("checkbox").checked = false;
jQuery (1.6+):
// Check
$("#checkbox").prop("checked", true);
// Uncheck
$("#checkbox").prop("checked", false);
jQuery (1.5...
How to copy an object in Objective-C
...es the same for all intents and purposes, but isn't (necessarily) a memory-identical clone of the original - the Objective C manual calls such an object "functionally independent" from it's original. Because the mechanisms for making these "intelligent" copies varies from class to class, we ask the ...
creating list of objects in Javascript
...
var list = [
{ date: '12/1/2011', reading: 3, id: 20055 },
{ date: '13/1/2011', reading: 5, id: 20053 },
{ date: '14/1/2011', reading: 6, id: 45652 }
];
and then access it:
alert(list[1].date);
...
javascript remove “disabled” attribute from html input
...
Set the element's disabled property to false:
document.getElementById('my-input-id').disabled = false;
If you're using jQuery, the equivalent would be:
$('#my-input-id').prop('disabled', false);
For several input fields, you may access them by class instead:
var inputs = document.getEl...
How can I create a copy of an object in Python?
...elf)(self.a, self.b)
def __deepcopy__(self, memo): # memo is a dict of id's to copies
id_self = id(self) # memoization avoids unnecesary recursion
_copy = memo.get(id_self)
if _copy is None:
_copy = type(self)(
deepcopy(self.a, memo),
...
Storyboard - refer to ViewController in AppDelegate
consider the following scenario: I have a storyboard-based app. I add a ViewController object to the storyboard, add the class files for this ViewController into the project and specify the name of the new class in the IB identity inspector. Now how am I going to refer to this ViewController program...