Social Networks for the life of the world
A version of this article specific to the Oracle DBMS is here. It’s often helpful to use SQL to group information by periods of time. For example, we might like to examine sales data. For example, we might have a table of individual sales transactions like so. Sales: sales_id int sales_time datetime net decimal(7,2) tax … Read more
It’s possible to use the geospatial extension in MySQL for an efficient location finder. For this to be worth the trouble, the following conditions must hold. You must use a MyISAM table for your geospatial data, or use version 5.7.5 or later of MySQL. A NOT NULL qualification on your geometry column is required A … Read more
In another article I described the process of using MySQL to compute great-circle distances between various points on the earth then their latitudes and longitudes are known. To do this requires the formula commonly called the haversine formula. It’s actually the spherical cosine law formula, and is shown here. There’s a more numerically stable formula — … Read more