SQL Fundamentals

Most web applications rely on storing their data in a relational database, consisting of tables which are comprised of columns and rows. PostgreSQL, MySQL and SQLite are the most popular and established relational databases, and luckily, they have a LOT in common.

SQL Fundamentals

Querying Across Tables

Time to put our newfound knowledge of relational algebra into practice! One of the great advantages of a relational database is the ability to mix tables together in queries, and aggregate or group across columns. Databases are built to do this kind of work, so it's often much faster to build the right query than to move similar logic into our application code.