SQL & databases

About this track

SQL is the language behind almost every application. Learn to read and write it here on Yanjye, with runnable examples against a small student database, then take the exam.

Every lesson is written and hosted here on Yanjye — you never leave the site. Work through them in order, then sit the exam to earn your certificate.

Create a free account or log in to track your progress and earn the certificate.

Lessons

1. 1
   What SQL is and how tables work

   Rows, columns and the shape of a database.

   ~15 min
2. 2
   SELECT and WHERE

   Read exactly the rows and columns you need.

   ~25 min
3. 3
   ORDER BY and LIMIT

   Sort your results and take only what you need.

   ~20 min
4. 4
   INSERT, UPDATE and DELETE

   Change the data, safely.

   ~30 min account needed
5. 5
   Aggregate functions

   Count, total and average your data.

   ~25 min account needed
6. 6
   GROUP BY and HAVING

   Summarise per category instead of over everything.

   ~25 min account needed
7. 7
   JOINs

   Combine related tables into one result.

   ~35 min account needed
8. 8
   Creating tables and keys

   Design a table that protects its own data.

   ~25 min account needed