Follow this step-by-step guide to install PostgreSQL, load data, connect to a database, and execute SQL queries including table joins PostgreSQL is an open-source, object-relational (also called ...

Read this SQL tutorial to learn when to use SELECT, JOIN, subselects and UNION to access multiple tables with a single statement. It’s sometimes difficult to know which SQL syntax to use when ...

A common SQL habit is to use SELECT * on a query, because it’s tedious to list all the columns you need. Plus, sometimes those columns may change over time, so why not just do things the easy way? But ...

Normalized data giving you problems? Learn how to use the SQL subselect statement and handle your database like a pro! Do you ever find yourself juggling queries to get the information you need?

Query federation is a way to make use of distributed data sources on the Web, including many SPARQL endpoints as well as relational databases. SWObjects makes use of mapping rules represented as ...