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Counting null and non-null values in a single query
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This works for Oracle and SQL Server (you might be able to get it to work on another RDBMS):
select sum(case when a is null then 1 else 0 end) count_nulls
, count(a) count_not_nulls
from us;
Or:
select count(*) - count(a), count(a) fro...
Is there a NumPy function to return the first index of something in an array?
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Yes, here is the answer given a NumPy array, array, and a value, item, to search for:
itemindex = numpy.where(array==item)
The result is a tuple with first all the row indices, then all the column indices.
For example, if an array is two dimensions and it contained your it...
Insert into a MySQL table or update if exists
...m what I've found, this method is less problematic for auto-increment keys and other unique key collisions than REPLACE INTO, and it is more efficient.
– Andrew Ensley
May 11 '12 at 21:27
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Error java.lang.OutOfMemoryError: GC overhead limit exceeded
...n excessive amount of time (by default 98% of all CPU time of the process) and recovers very little memory in each run (by default 2% of the heap).
This effectively means that your program stops doing any progress and is busy running only the garbage collection at all time.
To prevent your applica...
npm install vs. update - what's the difference?
What is the practical difference between npm install and npm update ? When should I use which?
5 Answers
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How to find list of possible words from a letter matrix [Boggle Solver]
...ictionary word that could be a solution must use only the grid's
# letters and have length >= 3. (With a case-insensitive match.)
import re
alphabet = ''.join(set(''.join(grid)))
bogglable = re.compile('[' + alphabet + ']{3,}$', re.I).match
words = set(word.rstrip('\n') for word in open('words')...
Regex - how to match everything except a particular pattern
...particular pattern? I'm faced with a situation where I have to match an (A and ~B) pattern.
8 Answers
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How to define a function in ghci across multiple lines?
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For guards (like your example), you can just put them all on one line and it works (guards do not care about spacing)
let abs n | n >= 0 = n | otherwise = -n
If you wanted to write your function with multiple definitions that pattern match on the arguments, like this:
fact 0 = 1
fact n =...
Error handling in getJSON calls
How can you handle errors in a getJSON call? Im trying to reference a cross-domain script service using jsonp, how do you register an error method?
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What is trunk, branch and tag in Subversion? [duplicate]
What is a trunk, branch and tag in Subversion and what are the best practices to use them?
9 Answers
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