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How do I perform an IF…THEN in an SQL SELECT?
...LSE <returndefaultcase>
END AS <newcolumnname>
FROM <table>
The extended case:
SELECT CASE WHEN <test> THEN <returnvalue>
WHEN <othertest> THEN <returnthis>
ELSE <returndefaultcase>
END AS ...
Split data frame string column into multiple columns
...
5 years later adding the obligatory data.table solution
library(data.table) ## v 1.9.6+
setDT(before)[, paste0("type", 1:2) := tstrsplit(type, "_and_")]
before
# attr type type1 type2
# 1: 1 foo_and_bar foo bar
# 2: 30 foo_and_bar_2 foo ba...
What's the difference between an inverted index and a plain old index?
...bove - a list of words, and where to find them in the book. In a book, the table of contents is like a forward index: it's a list of documents (chapters) which the book contains, except instead of listing the words in those sections, the table of contents just gives a name/general description of wha...
How does the socket API accept() function work?
...g on the Server IP maintains a database (meaning I don't care what kind of table/list/tree/array/magic data structure it uses) of active sockets and listens on the Server Port. When it receives a message (via the server's TCP/IP stack), it checks the Client IP and Port against the database. If the...
belongs_to through associations
...ter off caching the question_id on Choice and adding a unique index to the table (especially because validates_uniqueness_of is prone to race conditions).
If you're paranoid, add a custom validation to Choice that confirms that the answer's question_id matches, but it sounds like the end user shoul...
AngularJS ngClass conditional
...
Using ng-class inside ng-repeat
<table>
<tbody>
<tr ng-repeat="task in todos"
ng-class="{'warning': task.status == 'Hold' , 'success': task.status == 'Completed',
'active': task.status == 'Started', '...
Combine two ActiveRecord::Relation objects
...ny odd situations, by using Rails' built-in Arel.
User.where(
User.arel_table[:first_name].eq('Tobias').or(
User.arel_table[:last_name].eq('Fünke')
)
)
This merges both ActiveRecord relations by using Arel's or.
Merge, as was suggested here, didn't work for me. It dropped the 2nd set...
JPA: How to have one-to-many relation of the same Entity type
...both). But this resulted in a duplicate row being inserted into my Address table. Is this because I have misconfigured my CascadeType on the User's address field?
– Alex
Aug 25 '13 at 12:17
...
Is ASCII code 7-bit or 8-bit?
...
The original ASCII table is encoded on 7 bits therefore it has 128 characters.
Nowadays most readers/editors use an "extended" ASCII table (from ISO 8859-1), which is encoded on 8 bits and enjoys 256 characters (including Á, Ä, Œ, é, è an...
What is the difference between loose coupling and tight coupling in the object oriented paradigm?
...r", CustomerName);
}
}
class Database
{
public void AddRow(string Table, string Value)
{
}
}
Example of loose coupling:
class CustomerRepository
{
private readonly IDatabase database;
public CustomerRepository(IDatabase database)
{
this.database = database;
...