Sometimes you want to compute values automatically at
INSERT time, like for
example a
duration column out of a
start and an
end column, both
timestamptz. It’s easy enough to do with a
BEFORE TRIGGER on your table.
What’s more complex is to come up with a parametrized spelling of the
trigger, where you can attach the same
stored procedure to any table even
when the column names are different from one another.
There was SQL before window functions and SQL after window functions: that’s how powerful this tool is. Being that of a deal breaker unfortunately means that it can be quite hard to grasp the feature. This article aims at making it crystal clear so that you can begin using it today and are able to reason about it and recognize cases where you want to be using window functions.
In our recent article about The Most Popular Pub Names we did have a look at how to find the pubs nearby, but didn’t compute the distance in between that pub and us. That’s because how to compute a distance given a position on the earth expressed as longitude and latitude is not that easy. Today, we are going to solve that problem nonetheless, thanks to PostgreSQL Extensions.
In his article titled The Most Popular Pub Names Ross Lawley did show us how to perform some quite interesting geographic queries against MongoDB, using some nice Open Data found at the Open Street Map project.
In a recent article here we’ve been talking about how do do Batch Updates in a very efficient way, using the Writable CTE features available in PostgreSQL 9.1. I sometime read how Common Table Expressions changed the life of fellow DBAs and developers, and would say that Writable CTE are at least the same boost again.
