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CROSS JOIN vs INNER JOIN in SQL
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2. CROSS JOIN
Cross join selects the all the rows from the first table and all the rows from second table and shows as Cartesian product ie, with all possibilities
Consider we need to find all the teachers in the school and students irrespective of class teacher...
Find XOR of all numbers in a given range
You are given a large range [a,b] where 'a' and 'b' can be typically between 1 and 4,000,000,000 inclusive. You have to find out the XOR of all the numbers in the given range.
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Intellij IDEA, format all code in a project
I really like IDEA's code formatting, but how do I get it to reformat all the code in a particular project without going through each file? I've found the option to tidy / optimise imports on code before committing it to subversion which is great, but it only seems to apply to files that have otherw...
How can I use Google's Roboto font on a website?
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You don't really need to do any of this.
Go to Google's Web Fonts page
search for Roboto in the search box at the top right
Select the variants of the font you want to use
click 'Select This Font' at the top and choose the weights an...
Match everything except for specified strings
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Depends on the language, but there are generally negative-assertions you can put in like so:
(?!red|green|blue)
(Thanks for the syntax fix, the above is valid Java and Perl, YMMV)
share
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Simple explanation of MapReduce?
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Going all the way down to the basics for Map and Reduce.
Map is a function which "transforms" items in some kind of list to another kind of item and put them back in the same kind of list.
suppose I have a list of numbers: [1,2...
Does svn have a `revert-all` command?
If I want to throw away all of my changes, and return to the code that is on the repository, I do the following:
4 Answers
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Peak detection in a 2D array
...ood = generate_binary_structure(2,2)
#apply the local maximum filter; all pixel of maximal value
#in their neighborhood are set to 1
local_max = maximum_filter(image, footprint=neighborhood)==image
#local_max is a mask that contains the peaks we are
#looking for, but also the ...
in_array multiple values
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if(count(array_intersect($haystack, $target)) == count($target)){
// all of $target is in $haystack
}
Note that you only need to verify the size of the resulting intersection is the same size as the array of target values to say that $haystack is a superset of $target.
To verify that at lea...
SQL query return data from multiple tables
...I-89 syntax (and if you are used to 89, may seem much less intuitive - but all I can say is to try it) as it is much easier to understand when the queries start getting more complex. Why use it? Is there a performance gain? The short answer is no, but it is easier to read once you get used to it. It...