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Is the order guaranteed for the return of keys and values from a LinkedHashMap object?
I know LinkedHashMap has a predictable iteration order (insertion order). Does the Set returned by LinkedHashMap.keySet() and the Collection returned by LinkedHashMap.values() also maintain this order?
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What is the most efficient/elegant way to parse a flat table into a tree?
Assume you have a flat table that stores an ordered tree hierarchy:
14 Answers
14
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Select distinct values from a table field
...els.CharField(max_length=150)
# some of your models may have explicit ordering
class Meta:
ordering = ('city')
Since you may have the Meta class ordering attribute set, you can use order_by() without parameters to clear any ordering when using distinct(). See the documentation und...
How to use DISTINCT and ORDER BY in same SELECT statement?
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The problem is that the columns used in the ORDER BY aren't specified in the DISTINCT. To do this, you need to use an aggregate function to sort on, and use a GROUP BY to make the DISTINCT work.
Try something like this:
SELECT DISTINCT Category, MAX(CreationDate)
FR...
How to define a custom ORDER BY order in mySQL
In MySQL how do I define a custom sorting order.
4 Answers
4
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How to get last N records with activerecord?
...method:
Record.last(N)
Example:
User.last(5)
Returns 5 users in descending order by their id.
Deprecated (Old Answer)
An active record query like this I think would get you what you want ('Something' is the model name):
Something.find(:all, :order => "id desc", :limit => 5).reverse
edit: As n...
How to sort a dataframe by multiple column(s)
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You can use the order() function directly without resorting to add-on tools -- see this simpler answer which uses a trick right from the top of the example(order) code:
R> dd[with(dd, order(-z, b)), ]
b x y z
4 Low C 9 2
2 Med D 3 1
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How does MongoDB sort records when no sort order is specified?
When we run a Mongo find() query without any sort order specified, what does the database internally use to sort the results?
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C++11 introduced a standardized memory model. What does it mean? And how is it going to affect C++ p
...ot even say anything about the atomicity of memory loads and stores or the order in which loads and stores might happen, never mind things like mutexes.
Of course, you can write multi-threaded code in practice for particular concrete systems – like pthreads or Windows. But there is no standard w...
Order of serialized fields using JSON.NET
Is there a way to specify the order of fields in a serialized JSON object using JSON.NET ?
14 Answers
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