Course description

Tired of waiting for someone to send you a spreadsheet export? This course teaches you to ask your own questions of a database with SQL, from your very first SELECT to joins, summaries and rankings you can hand to your manager. You'll use DB Browser for SQLite, a free program for Windows and Mac, and a database holding a full year of a fictional nursery's sales, so every query you write gives an exact answer you can check.

It's a full course, not a quick tour. There are 10 sections and 50 written lessons, each with queries you can copy, their exact results and exercises to try yourself. You follow a fictional customer services coordinator at a plant nursery in Rutland as she learns SQL to answer the owner's questions, with the mistakes she made and how she fixed them. Every section has a practice pack with the database, exercise and solution files, expected results and a cheat sheet.

What you'll learn

• Getting started: what a database is, installing DB Browser for SQLite, tables, keys and your first SELECT.
• Filtering: WHERE, AND, OR, IN, BETWEEN, LIKE and handling missing values (NULL) properly.
• Sorting and calculating: ORDER BY, LIMIT, calculated columns, text functions and CASE.
• Dates: pulling out years, months and weekdays, date arithmetic and filtering by date safely.
• Summaries: COUNT, SUM, AVG, GROUP BY and HAVING, and how to make sure your totals add up.
• Joins: INNER JOIN and LEFT JOIN, joining several tables and avoiding inflated totals.
• Subqueries and CTEs: queries inside queries, WITH, UNION and EXISTS.
• Window functions and views: rankings, running totals, month-on-month change and saved queries.
• Changing data: CREATE TABLE, INSERT, UPDATE and DELETE safely, importing and exporting CSV files and good table design.

The final project

You'll build a complete review of a year's trading in one SQL file: sales by shop, month and category, customers and loyalty, best and worst products, returns and gross profit. Then you'll check your figures against the model results and write up what they mean in plain English.

Who this course is for

• Office workers and analysts who live in spreadsheets and want to work with databases directly.
• Anyone starting a data, reporting or junior analyst role where SQL is expected.
• Small business owners and team leaders who want answers from their own sales or customer data.

How the course works

Read each lesson, run the queries in DB Browser for SQLite and compare your results with the ones in the lesson. No coding experience is needed. The SQL you learn works in other database systems too, with small differences that the last section explains. You keep lifetime access, so you can come back whenever you need a reminder.

What will I learn?

• Open a database in DB Browser for SQLite and understand tables, columns, keys and data types
• Write SELECT queries that filter, sort and calculate, including handling missing values (NULL) correctly
• Work with dates to answer questions by year, month and weekday
• Summarise data with COUNT, SUM, AVG, GROUP BY and HAVING, and check that totals add up
• Combine tables with INNER JOIN and LEFT JOIN without inflating your figures
• Use subqueries, common table expressions (WITH) and EXISTS to answer multi-step questions
• Rank, compare and build running totals with window functions, and save queries as views
• Create tables, import CSV files and change data safely with INSERT, UPDATE, DELETE and transactions

Frequently asked questions