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Difference between EXISTS and IN in SQL?
...e [field] in (1, 2, 3)
When you have a table in an in statement it makes more sense to use a join, but mostly it shouldn't matter. The query optimiser should return the same plan either way. In some implementations (mostly older, such as Microsoft SQL Server 2000) in queries will always get a nest...
Control cannot fall through from one case label
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Is the “struct hack” technically undefined behavior?
...ous pointer arithmetic could then be made to trap - see e.g. CCured. On a more philosophical level, it doesn't matter whether no possible implementation could catch you, it's still undefined behavior (there are, iirc, cases of undefined behavior that would require an oracle for the Halting Problem ...
How to create a self-signed certificate for a domain name for development?
...t for makecert.exe to be in my path. For the certificates I thought I'd be more secure and use -a SHA512 -len 8192 -- it took forever to generate. And as I suspected it might, it had zero impact on what level of encryption IIS used. By default IIS uses 128-bit, you have to do group policy stuff to c...
When to use lambda, when to use Proc.new?
...e proc itself
In a Proc.new-created proc, the return statement is a little more surprising: it returns control not just from the proc, but also from the method enclosing the proc!
Here's lambda-created proc's return in action. It behaves in a way that you probably expect:
def whowouldwin
mylam...
Does the join order matter in SQL?
... FULL) OUTER joins, yes, the order matters - and (updated) things are much more complicated.
First, outer joins are not commutative, so a LEFT JOIN b is not the same as b LEFT JOIN a
Outer joins are not associative either, so in your examples which involve both (commutativity and associativity) pr...
Why are variables “i” and “j” used for counters?
... That's a good question. I actually think that "i" might come from integer more than index. I also think it's easy to write on a chalkboard. Back in the 70's we were cautioned to be sure that we wrote our "i" and "j" in a perfectly distinctive manner. Indeed, we were told to draw our "i" exactly ...
How to return an empty ActiveRecord relation?
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How to retrieve a single file from a specific revision in Git?
...oot of the repository, not your current directory position.
(Although Mike Morearty mentions that, at least with git 1.7.5.4, you can specify a relative path by putting "./" at the beginning of the path. For example:
git show HEAD^^:./test.py
)
Using git restore
With Git 2.23+ (August 2019), you ca...
Generating random strings with T-SQL
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