courses / sql
learn sql
Three levels, from never written code to writing it like a professional. Ask questions of databases.
from zero to your first real programs.
For people who have never written a line of code. Nothing is assumed: every new word is explained the moment it appears.
1 unit 1 Meet your data Ask a database to show you what it holds.
2 unit 2 Pick your rows Ask for only the rows you need.
3 unit 3 Sort and trim Put results in order and keep only the bits you want.
4 unit 4 Blanks, maths and text Handle missing values and work out new ones.
5 unit 5 Sum it up Turn a whole table into one answer.
6 unit 6 Change the data Add, change and remove rows.
7 unit 7 Build your own tables Make your own tables, then put everything together.
build things that are actually useful.
For people who finished Level 1, or can already write small programs with variables, decisions, loops and functions.
1 unit 1 Groups and totals Get one answer for every group, not one for the whole table.
2 unit 2 Join tables together Store each fact once, link tables by id, then bring them back together.
3 unit 3 More joins Keep rows with no match, find what is missing and join three tables.
4 unit 4 Queries inside queries Check values against lists, and use one query's answer inside another.
5 unit 5 Choose with CASE Make a query choose a value for every row, and fill in the blanks.
6 unit 6 Rules that protect your data Let the database refuse bad data before it ever gets in.
7 unit 7 Design and dates Link tables many to many, work with dates, then build a full report.
write sql like a professional.
For people who build things on their own and want code that others trust and can change.