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Articles about the MySQL relational data management system.
Have you been around long enough to remember the Kermit terminal program? It was a very important way of getting online in the late 1980s and early 1990s. Frank da Cruz, Kermit’s creator, also has an interest in world languages and Unicode. He put together a terrific web page containing samples of text in many languages. … Read more
It’s common in database work to need unique integers. They get used in id columns in tables, and for other purposes. This note compares and contrasts the Oracle and MySQL approaches to doing this. MySQL handles this need with autoincrement columns, in tables and Oracle handles it with database objects called sequences. In MySQL, when … Read more
I’ve spent enough time goofing around with location-finder software that it’s worth writing up how to do it. Of course, finding distances on the surface of the earth means using Great Circle distances, worked out with the Haversine formula, also called the Spherical Cosine Law formula. The problem is this: Given a table of … Read more
This MySQL Stored Function computes the initial bearing — the compass heading to follow — when moving from one point to another on the surface of the earth. Here’s a web site describing this. http://www.movable-type.co.uk/scripts/latlong.html
When you’re extracting summaries of information from a database, sometimes rows are missing. For example, if you are keeping track of number of customers by day, you might use a query like this: View the code on Gist. You might get a result set like this: 2014-03-07 122 2014-03-08 355 2014-03-10 234 2014-03-11 119 Notice … Read more
Finally! Automattic and WordPress are starting to retire the old mysql data-access API. This is going to foul up WordPress themes and plugins that use those APIs. It shouldn’t be hard to switch. For a while there’s been a global instance of the WPDB class that developers can use. Gary Pendergast has a good article … Read more
Check this out: Disasters resulting from bad numerical computing. Be careful when messing around with FLOAT, DOUBLE, and INTEGER data. For want of a bit …
Check out this compendium of useful query patterns for MySQL
Sometimes learning to use data systems like MySQL means you need to get your hands on various publicly available sets of data. Here are some sources. Pro Publica, the investigative news powerhouse, has a Data Store. It’s mostly health care related material. Not all their datasets are free, but some are. If you’re interested in … Read more
This Vincenty formula is a more numerically stable version of the spherical cosine law formula (commonly and wrongly known as the Haversine formula) for computing great circle distances. The question of numerical stability comes up specifically when the distances between points are small. In those cases the cosine is very close to 1, so the … Read more
