postgres

Sigh, so many broken links, so little time ... when I switched this website to Drupal, I didn't (couldn't) take the time to move all of my static content in the Drupal CMS, so a lot of great content is just sitting out there in static files. To help fix that problem a little bit, here's a link to a collection of Java test project (example projects) that demonstrate all sorts of cool and fun things with Java, including:

Here's a quick demonstration of how to create a Tomcat connection pool (database connection pool) using the Tomcat DBCP library.

I'm not going to go into a detailed explanation here of how Tomcat DBCP works, other than to say that it works for me, and I've tried to include everything here that you'll need to implement your own Tomcat DBCP database connection pool in your web applications.

I just ran into a crazy error related to Tomcat and DBCP connection pooling. The error message I got after trying to use the Tomcat DBCP connection pooling in my Java web application was:

Okay, maybe this is lame, but when I've been away from writing SQL database queries for a while I can never remember how to search for database table fields that are either NULL, or NOT NULL. I always try to use the = operator or something else.

So, for you Al, here's how to perform a SQL query and find all records where a field in a database table is NULL:

SELECT * FROM foo WHERE bar IS NULL;

And here's how to perform a SQL query showing all records in a database table where a field is NOT NULL:

If you get a Postgresql error message like this:

ERROR:  must be owner of relation [your_table_here]

don't worry too much, it probably means what it says: You don't own the table (or relation) you're trying to modify. Well, I guess you can worry if you can't get someone to fix the permissions, but if you can it's no big deal.