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General suggestions for debugging in R
...orite debugging routine:
When an error occurs, the first thing that I usually do is look at the stack trace by calling traceback(): that shows you where the error occurred, which is especially useful if you have several nested functions.
Next I will set options(error=recover); this immediately sw...
What are the pros and cons of performing calculations in sql vs. in your application
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It depends on a lot of factors - but most crucially:
complexity of calculations (prefer doing complex crunching on an app-server, since that scales out; rather than a db server, which scales up)
volume of data (if you need to access/aggregate a lot of data, doing it at ...
Android: Storing username and password?
...how to use it.
If this is not an option to you for some reason, you can fall back to persisting credentials using the Preferences mechanism. Other applications won't be able to access your preferences, so the user's information is not easily exposed.
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How can I check if a View exists in a Database?
...oc msdn.microsoft.com/en-us/library/ms190328.aspx - and this one gives you all the object types : msdn.microsoft.com/en-us/library/ms190324.aspx
– Simon_Weaver
May 26 '16 at 7:04
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postgresql return 0 if returned value is null
...ns the first of its arguments that is not null.
Null is returned only if all arguments are null. It is often
used to substitute a default value for null values when data is
retrieved for display.
Edit
Here's an example of COALESCE with your query:
SELECT AVG( price )
FROM(
SELECT *, cum...
Set up a scheduled job?
...Django, and I'm curious if there is a way to schedule a job to run periodically.
24 Answers
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Counting null and non-null values in a single query
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If I understood correctly you want to count all NULL and all NOT NULL in a column...
If that is correct:
SELECT count(*) FROM us WHERE a IS NULL
UNION ALL
SELECT count(*) FROM us WHERE a IS NOT NULL
Edited to have the full query, after reading the comments :]
S...
How does a Java HashMap handle different objects with the same hash code?
...ng bucket, and then it will compare the key that you gave with the keys of all pairs in the bucket, by comparing them with equals().
Now you can see how this is very efficient for looking up key-value pairs in a map: by the hash code of the key the hashmap immediately knows in which bucket to look,...
Using Laravel Homestead: 'no input file specified'
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Instead of reinstalling try
vagrant up --provision
or
homestead up --provision
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Go to back directory browsing after opening file in vim
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Nice thing summarizing all the other correct answers, I wish more people do that.
– LightMan
Jul 19 '18 at 8:57
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