For working with data yourself
5 chapters · 10 lessonsAbout 1 h
A free, hands-on SQL course you can run in your browser. Connect to a database that behaves just like PostgreSQL, look around, and pull out exactly the rows you need.
This course continues from Database Introduction
SQL is how you tell a database which rows you want. Whether you build apps or read numbers, it is the same language.
This course uses one small online shop database from the first lesson to the last. Reading the same tables again and again is what makes the shapes stick.
The database in the exercises is a simulation running in your browser, checked byte for byte against real PostgreSQL 17 output. Even the error messages match, so what you learn to read here reads the same at work.
Connect, see which tables exist, and read their columns and types.
Filter, sort, and limit, so you get exactly the rows you were after.
Learn the routine that lets you undo a change you did not mean to make.
Read and write the tables from Database Introduction, now with SQL you write yourself.
Connect yourself and pull out exactly the rows you need.
Try the parts people get wrong the most, NULL and joins, and see what actually happens.
5 chapters · 10 lessons
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