Databases & Data
Learn SQL
SQL is the language used to ask questions of a relational database and to change the data it holds. You describe what you want, and the database works out how to fetch it.
Why teams use it
- Almost every business application stores its core data in a relational database.
- Being able to read and write SQL is what lets you verify what your application actually did.
- Understanding queries is the difference between a page that loads in 50ms and one that takes 5 seconds.
Where you will meet it
When a report is slow, the fix is usually in the query or an index, not in the application code around it.
What to learn, and in what order
Work through these roughly in order. Jumping to the advanced list before the basics are solid is the most common way people get stuck.
Beginner
- Tables, rows, columns and keys
- SELECT, WHERE and ORDER BY
- INSERT, UPDATE and DELETE
- Relationships between tables
Intermediate
- Joins in depth
- Grouping and aggregation
- Subqueries and common table expressions
- Views, functions and stored procedures
- Transactions and isolation
Advanced
- Indexes and how they are chosen
- Reading execution plans
- Query tuning
- Normalization and schema design trade-offs
Have a project worth talking through?
Tell us what you're building or what's slowing your current system down. We'll give you a direct read on scope and approach.