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Select first row in each GROUP BY group?
...d by any database:
But you need to add logic to break ties:
SELECT MIN(x.id), -- change to MAX if you want the highest
x.customer,
x.total
FROM PURCHASES x
JOIN (SELECT p.customer,
MAX(total) AS max_total
FROM PURCHASES p
GROUP BY ...
Get the client's IP address in socket.io
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@GarciadelCastillo you are behind a proxy probably. try this: stackoverflow.com/a/11187053/971459
– Samson
Jun 25 '13 at 9:30
4
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Can't update Macports (with Mac OS X Mavericks)
After upgrading Mac OS X to newest version Mavericks, I attempted to selfupdate my Macports, but it failed:
9 Answers
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Current time formatting with Javascript
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A JavaScript Date has several methods allowing you to extract its parts:
getFullYear() - Returns the 4-digit year
getMonth() - Returns a zero-based integer (0-11) representing the month of the year.
getDate() - Returns the day of the month (1-31).
getDay() - Returns the day of t...
How do you know when to use fold-left and when to use fold-right?
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You can transfer a fold into an infix operator notation (writing in between):
This example fold using the accumulator function x
fold x [A, B, C, D]
thus equals
A x B x C x D
Now you just have to reason about the associativity of your operator (by puttin...
Explain the encapsulated anonymous function syntax
Can you explain the reasoning behind the syntax for encapsulated anonymous functions in JavaScript? Why does this work: (function(){})(); but this doesn't: function(){}(); ?
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Locate Git installation folder on Mac OS X
I'm just curious, Where Git get installed (via DMG) on Mac OS X file system?
11 Answers
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Replace all whitespace characters
...v\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]
in Firefox and [ \f\n\r\t\v] in IE.
str = str.replace(/\s/g, "X");
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How do I combine two data-frames based on two columns? [duplicate]
...both have,
but separate specifications of the columns can be given by by.x and by.y.
This clearly implies that merge will merge data frames based on more than one column. From the final example given in the documentation:
x <- data.frame(k1=c(NA,NA,3,4,5), k2=c(1,NA,NA,4,5), data=1:5)
y <...