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SQL UPDATE SET one column to be equal to a value in a related table referenced by a different column
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Without the update-and-join notation (not all DBMS support that), use:
UPDATE QuestionTrackings
SET QuestionID = (SELECT QuestionID
FROM AnswerTrackings
WHERE AnswerTrackings.AnswerID = QuestionTrackings.AnswerID)
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Advantages to Using Private Static Methods
When creating a class that has internal private methods, usually to reduce code duplication, that don't require the use of any instance fields, are there performance or memory advantages to declaring the method as static?
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How to check 'undefined' value in jQuery
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JQuery library was developed specifically to simplify and to unify certain JavaScript functionality.
However if you need to check a variable against undefined value, there is no need to invent any special method, since JavaScript has a typeof operator, which is...
Symbolic links and synced folders in Vagrant
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Virtualbox does not allow symlinks on shared folders for security reasons. To enable symlinks the following line needs to be added to the vm provider config block in the Vagrantfile:
config.vm.provider "virtualbox" do |v|
v.customize ["sete...
How to set JAVA_HOME in Linux for all users
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For all users, I would recommend placing the following line in /etc/profile
export JAVA_HOME=$(readlink -f /usr/bin/javac | sed "s:/bin/javac::")
This will update dynamically and works well with the alternatives system. Do not...
Hidden features of Perl?
What are some really useful but esoteric language features in Perl that you've actually been able to employ to do useful work?
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How to determine a Python variable's type?
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It is so simple. You do it like this.
print(type(variable_name))
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Find the most common element in a list
...roups by the item only (via operator.itemgetter). The auxiliary function, called once per grouping during the max computation, receives and internally unpacks a group - a tuple with two items (item, iterable) where the iterable's items are also two-item tuples, (item, original index) [[the items of ...
Python's json module, converts int dictionary keys to strings
...which implement a __hash__ method. (The Lua docs suggest that it automatically uses the object's ID as a hash/key even for mutable objects and relies on string interning to ensure that equivalent strings map to the same objects).
In Perl, Javascript, awk and many other languages the keys for hash...
assertEquals vs. assertEqual in python
...as been deprecated as well:
Method Name | Deprecated alias(es)
_________________________________________________________
assertEqual() | failUnlessEqual, assertEquals
From 25.3.7.1.1. Deprecated aliases
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