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Understanding exactly when a data.table is a reference to (vs a copy of) another data.table
I'm having a little trouble understanding the pass-by-reference properties of data.table . Some operations seem to 'break' the reference, and I'd like to understand exactly what's happening.
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SQL Server insert if not exists best practice
I have a Competitions results table which holds team member's names and their ranking on one hand.
8 Answers
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Relational Database Design Patterns? [closed]
...lated to object oriented design.
Are there design patterns for creating and programming relational databases?
Many problems surely must have reusable solutions.
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Can we write our own iterator in Java?
If I have a list containing [alice, bob, abigail, charlie] and I want to write an iterator such that it iterates over elements that begin with 'a', can I write my own ? How can I do that ?
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Class.forName() vs ClassLoader.loadClass() - which to use for dynamic loading? [duplicate]
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(true here refers to do you want to initialize the class?)
On the other hand, ClassLoader.loadClass(String):
Invoking this method is equivalent to invoking loadClass(name, false).
(here, the boolean has nothing to do with initialization; but if you check loadClass(String, boolean) documentat...
Do I encode ampersands in ?
I'm writing code that automatically generates HTML, and I want it to encode things properly.
4 Answers
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How can I reverse the order of lines in a file?
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BSD tail:
tail -r myfile.txt
Reference: FreeBSD, NetBSD, OpenBSD and OS X manual pages.
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How do you delete an ActiveRecord object?
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It's destroy and destroy_all methods, like
user.destroy
User.find(15).destroy
User.destroy(15)
User.where(age: 20).destroy_all
User.destroy_all(age: 20)
Alternatively you can use delete and delete_all which won't enforce :before_destro...
How to get .pem file from .key and .crt files?
...ust named with .crt or .key.
If the file's content begins with -----BEGIN and you can read it in a text editor:
The file uses base64, which is readable in ASCII, not binary format. The certificate is already in PEM format. Just change the extension to .pem.
If the file is in binary:
For the serv...
Why are margin/padding percentages in CSS always calculated against width?
... Since the
height of the child is dependent on the height of the parent, and the
height of the parent is dependent on the height of the child, we'll
either have inaccurate height, or an infinite loop. Sure, this only
affects the case where offset parent === parent, but still. It's an
odd c...