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How do SQL EXISTS statements work?
...hen tries to match this 'true/false' condition with outerquery." is what really cleared it up for me, I keep thinking that's how subqueries work (and many times they do), but what you said makes sense because the subquery relies on the outer query and therefore must be executed once per row
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Showing line numbers in IPython/Jupyter Notebooks
...l line numbers. In more recent notebook versions Shift-L should toggle for all cells.
If you can't remember the shortcut, bring up the command palette Ctrl-Shift+P (Cmd+Shift+P on Mac), and search for "line numbers"), it should allow to toggle and show you the shortcut.
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What is the difference between $(command) and `command` in shell programming?
... for portability issues it is recommended to use backticks for non-nested calls. $(...) needs a recursive parser but this was not used with ksh86 that introduced the feature. Check in-ulm.de/~mascheck/various/cmd-subst for a list of correct implementations. A conforming shell needs to support all c...
git reset --hard HEAD leaves untracked files behind
...rking copy.
If you need to reset the whole repository to master including all git submodules, run this script:
git reset --hard HEAD
git clean -f -d
git checkout master
git fetch origin master
git reset --hard origin/master
git pull
git submodule update
git submodule update --init --recursive
git ...
What online brokers offer APIs? [closed]
So I'm getting really sick of E*TRADE and, being a developer, would love to find an online broker that offers an API. It would be great to be able to write my own trading tools, and maybe even modify existing ones.
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How to get a list of installed Jenkins plugins with name and version pair
How can I get a list of installed Jenkins plugins?
21 Answers
21
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Advantages of stateless programming?
I've recently been learning about functional programming (specifically Haskell, but I've gone through tutorials on Lisp and Erlang as well). While I found the concepts very enlightening, I still don't see the practical side of the "no side effects" concept. What are the practical advantages of it? ...
Are braces necessary in one-line statements in JavaScript?
... expands the statement it will be required.
This same practice follows in all C syntax style languages with bracing. C, C++, Java, even PHP all support one line statement without braces. You have to realize that you are only saving two characters and with some people's bracing styles you aren't eve...
JOIN queries vs multiple queries
...ase. It depends on a lot of things. Jeff Atwood (founder of this site) actually wrote about this. For the most part, though, if you have the right indexes and you properly do your JOINs it is usually going to be faster to do 1 trip than several.
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Why is it necessary to set the prototype constructor?
...};
// define the Student class
function Student(name) {
Person.call(this, name);
}
// inherit Person
Student.prototype = Object.create(Person.prototype);
Now what happens when we create a new Student and copy it?
var student1 = new Student("trinth");
console.log(student1....