Sample text in many languages

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

Unique Numbers in Oracle and MySQL

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

Fast nearest-location finder for SQL (MySQL, PostgreSQL, SQL Server)

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

Computing an initial bearing

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

Filling in missing data with sequences of cardinal integers

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

Publicly Available Datasets

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

The Vincenty great-circle distance formula

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