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Why do you create a View in a database?
...base in which some of the entities were person, company, role, owner type, order, order detail, address and phone, where the person table stored both employees and contacts and the address and phone tables stored phone numbers for both persons and companies, and the development team were tasked with...
How to pull a random record using Django's ORM?
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Using order_by('?') will kill the db server on the second day in production. A better way is something like what is described in Getting a random row from a relational database.
from django.db.models.aggregates import Count
from r...
How to install trusted CA certificate on Android device?
...website:
As of Android N, you need to add configuration to your app in order to
have it trust the SSL certificates generated by Charles SSL Proxying.
This means that you can only use SSL Proxying with apps that you
control.
In order to configure your app to trust Charles, you need to ...
Dynamically select data frame columns using $ and a character value
...the second is a data.frame
mtcars[[var]]
mtcars[var]
You can perform the ordering without loops, using do.call to construct the call to order. Here is a reproducible example below:
# set seed for reproducibility
set.seed(123)
df <- data.frame( col1 = sample(5,10,repl=T) , col2 = sample(5,10,r...
Why would anyone use set instead of unordered_set?
C++0x is introducing unordered_set which is available in boost and many other places. What I understand is that unordered_set is hash table with O(1) lookup complexity. On the other hand, set is nothing but a tree with log(n) lookup complexity. Why on earth would anyone use set instead ...
Is the order of elements in a JSON list preserved?
I've noticed the order of elements in a JSON object not being the original order.
5 Answers
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Case objects vs Enumerations in Scala
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The other difference is that Enumeration enum is ordered out of the box, whereas case object based enum obviosly not
– om-nom-nom
Oct 18 '12 at 11:48
1
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Hashset vs Treeset
... log-time for most operations like add, remove and contains) but offers no ordering guarantees like TreeSet.
HashSet
the class offers constant time performance for the basic operations (add, remove, contains and size).
it does not guarantee that the order of elements will remain constant over ti...
Converting dict to OrderedDict
I am having some trouble using the collections.OrderedDict class. I am using Python 2.7 on Raspbian, the Debian distro for Raspberry Pi. I am trying to print two dictionaries in order for comparison (side-by-side) for a text-adventure. The order is essential to compare accurately.
No matter what I...
Why use the INCLUDE clause when creating an index?
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If the column is not in the WHERE/JOIN/GROUP BY/ORDER BY, but only in the column list in the SELECT clause.
The INCLUDE clause adds the data at the lowest/leaf level, rather than in the index tree.
This makes the index smaller because it's not part of the tree
INCLUDE co...