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Add Foreign Key to existing table
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To add a foreign key (grade_id) to an existing table (users), follow the following steps:
ALTER TABLE users ADD grade_id SMALLINT UNSIGNED NOT NULL DEFAULT 0;
ALTER TABLE users ADD CONSTRAINT fk_grade_id FOREIGN KEY (grade_id) REFERENCES grades(id);
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Convert a float64 to an int in Go
...problem in Go that can be unexpected (at least if you come from Java): "In all non-constant conversions involving floating-point or complex values, if the result type cannot represent the value the conversion succeeds but the result value is implementation-dependent." (golang.org/ref/spec#Conversion...
Debug vs Release in CMake
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With CMake, it's generally recommended to do an "out of source" build. Create your CMakeLists.txt in the root of your project. Then from the root of your project:
mkdir Release
cd Release
cmake -DCMAKE_BUILD_TYPE=Release ..
make
And for Debug (...
Meaning of 'const' last in a function declaration of a class?
...e that is often broken and easily broken.
foobar& fbNonConst = const_cast<foobar&>(fb1);
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Property getters and setters
...g to backup the computed property. Try this:
class Point {
private var _x: Int = 0 // _x -> backingX
var x: Int {
set { _x = 2 * newValue }
get { return _x / 2 }
}
}
Specifically, in the Swift REPL:
15> var pt = Point()
pt: Point = {
_x = 0
}
16> pt.x = 10...
How do I clone a Django model instance object and save it to the database?
...imary key of your object and run save().
obj = Foo.objects.get(pk=<some_existing_pk>)
obj.pk = None
obj.save()
If you want auto-generated key, set the new key to None.
More on UPDATE/INSERT here.
Official docs on copying model instances: https://docs.djangoproject.com/en/2.2/topics/db/que...
Way to ng-repeat defined number of times instead of repeating over array?
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Update (9/25/2018)
Newer versions of AngularJS (>= 1.3.0) allow you to do this with only a variable (no function needed):
<li ng-repeat="x in [].constructor(number) track by $index">
<span>{{ $index+1 }}</span>
</li>
$scope.number = 5;
This was not poss...
Is it possible to use argsort in descending order?
... this method is that ids is a view of avgDists:
>>> ids.flags
C_CONTIGUOUS : False
F_CONTIGUOUS : False
OWNDATA : False
WRITEABLE : True
ALIGNED : True
UPDATEIFCOPY : False
(The 'OWNDATA' being False indicates this is a view, not a copy)
Another way to do this is something ...
Making macOS Installer Packages which are Developer ID ready
Note: This is for OS X Installer packages only, packages for submission to the Mac App Store follow different rules.
5 ...
What's the difference between %s and %d in Python string formatting?
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what do you call these %s, %d, etc?
– Chaine
May 19 '17 at 18:21
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