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What is the difference between a database and a data warehouse?
... as Data Warehousing. This records the data from the user for history.
The tables and joins are complex since they are normalized (for RDMS). This is done to reduce redundant data and to save storage space.
Entity – Relational modeling techniques are used for RDMS database design.
Optimized for wr...
Factors in R: more than an annoyance?
...a pain, but my theory is that 90% of why they're a pain is because in read.table and read.csv, the argument stringsAsFactors = TRUE by default (and most users miss this subtlety). I say they are useful because model fitting packages like lme4 use factors and ordered factors to differentially fit mod...
How to return an empty ActiveRecord relation?
...
A more portable solution that doesn't require an "id" column and doesn't assume there won't be a row with an id of 0:
scope :none, where("1 = 0")
I'm still looking for a more "correct" way.
...
Design Pattern for Undo Engine
...e object is needed, you lookup the current definition of the object from a table. The table contains a linked list for each object that contains all the previous versions, along with information regarding which checkpoint they were active for.
Implementing undo/redo is simple: Do your action and es...
LEFT OUTER joins in Rails 3
... the :include option, which will perform an
INNER JOIN on the associated table(s), or an array containing a
mixture of both strings and named associations.
If the value is a
string, then the records will be returned read-only since they will
have attributes that do not correspond to th...
Test if lists share any items in python
...as such:
bool(set(a) & set(b))
Because sets are stored using a hash table in Python, searching them is O(1) (see here for more information about complexity of operators in Python). Theoretically, this is O(n+m) on average for n and m objects in lists a and b. But 1) it must first create sets ...
String literals and escape characters in postgresql
Attempting to insert an escape character into a table results in a warning.
5 Answers
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How can I call a custom Django manage.py command directly from a test driver?
...for a Django manage.py command that does a backend operation on a database table. How would I invoke the management command directly from code?
...
PDO's query vs execute
... execution. Which means you can do:
$sth = $db->prepare("SELECT * FROM table WHERE foo = ?");
$sth->execute(array(1));
$results = $sth->fetchAll(PDO::FETCH_ASSOC);
$sth->execute(array(2));
$results = $sth->fetchAll(PDO::FETCH_ASSOC);
They generally will give you a performance impr...
Why does Sql Server keep executing after raiserror when xact_abort is on?
...nd executes a stored procedure that we assume will fail:
assume we have a table [dbo].[Errors] to hold errors
assume we have a stored procedure [dbo].[AssumeThisFails] which will fail when we execute it
-- first lets build a temporary table to hold errors
if (object_id('tempdb..#RAISERRORS') is nu...