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What's wrong with nullable columns in composite primary keys?
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Primary keys are for uniquely identifying rows. This is done by comparing all parts of a key to the input.
Per definition, NULL cannot be part of a successful comparison. Even a comparison to itself (NULL = NULL) will fail. This means a key containing NULL would not work.
Additonally, NULL is al...
How to pretty print nested dictionaries?
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This is cool, but doesn't print all dictionaries well. print json.dumps(myObject.__dict__, sort_keys=True, indent=4) #TypeError: <object at 0x0000000002E6A748> is not JSON serializable
– tponthieux
Feb 8 '12 at 2...
Pass complex parameters to [Theory]
... InlineData attributes, and xUnit will generate many tests, and test them all.
8 Answers
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两种js滑动门(tab切换)效果 - 源码下载 - 清泛网 - 专注C/C++及内核技术
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thisObj.className = "active";
document.getElementById(tabObj+"_Content"+i).style.display = "block";
}else{
tabList[i].className = "normal";
document.getElementById(tabObj+"_Content"+i).style.display = "none";
}
}
}
</script>
</head>
<body>
<div align...
How can I change the color of pagination dots of UIPageControl?
... f = CGRectMake(0, 0, 320, 20);
PageControl *pageControl = [[[PageControl alloc] initWithFrame:f] autorelease];
pageControl.numberOfPages = 10;
pageControl.currentPage = 5;
pageControl.delegate = self;
[self addSubview:pageControl];
Header file:
//
// PageControl.h
//
// Replacement for UIPage...
Python mysqldb: Library not loaded: libmysqlclient.18.dylib
I just compiled and installed mysqldb for python 2.7 on my mac os 10.6. I created a simple test file that imports
15 Answe...
Why do we need a pure virtual destructor in C++?
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Probably the real reason that pure virtual destructors are allowed is that to prohibit them would mean adding another rule to the language and there's no need for this rule since no ill-effects can come from allowing a pure virtual destructor.
Nope, plain old virtual is enough.
If...
What is the difference between an interface and abstract class?
...'t do anything. It's just a pattern.
For example (pseudo code):
// I say all motor vehicles should look like this:
interface MotorVehicle
{
void run();
int getFuel();
}
// My team mate complies and writes vehicle looking that way
class Car implements MotorVehicle
{
int fuel;
vo...
How can sbt pull dependency artifacts from git?
... myProject = Project("my-project", file("."))
.settings(myProjectSettings: _*)
.dependsOn(Projects.depProject)
.settings(
libraryDependencies ++= Seq(...
Note that if you have multiple SBT projects dependending on the same external project, it's worth setting up a central sbt.boot.directory to a...
Is it possible to get the non-enumerable inherited property names of an object?
... use that and combine it with walking up the prototype chain.
function getAllProperties(obj){
var allProps = []
, curr = obj
do{
var props = Object.getOwnPropertyNames(curr)
props.forEach(function(prop){
if (allProps.indexOf(prop) === -1)
al...