Beautiful Charts in R with ggplot2 (for Excel Users)
Build bar, line and scatter charts in R with ggplot2, and learn the “grammar of graphics” idea that makes every chart the same few…
Read article →Coding
Start-to-finish programming for people who work with data: Python, SQL, Java, R, JavaScript, Rust and PowerShell.
SQL Lesson 12: Project — A Sales Report in SQL
SQL Lesson 12: Project — A Sales Report in SQL
Put the course together: build a half-year sales report from shop.db with total sales, GST, top customer, best month, cancellation rate and a region…
Read article →SQL Lesson 11: Views
SQL Lesson 11: Views
Save a query as a view: build an order_lines view joining orders, customers and products, query it like a table, use views for reports…
Read article →SQL Lesson 10: INSERT, UPDATE and DELETE Safely
SQL Lesson 10: INSERT, UPDATE and DELETE Safely
Change data without disasters: INSERT rows, UPDATE with a WHERE you have tested, DELETE carefully, transactions with BEGIN/ROLLBACK/COMMIT, and habits that prevent “I updated…
Read article →SQL Lesson 9: Working With Dates
SQL Lesson 9: Working With Dates
Filter and group by dates in SQL: ISO date format, month and year ranges, strftime/date functions in SQLite (and SQL Server/PostgreSQL equivalents), adding days,…
Read article →SQL Lesson 8: CASE — If-Then in SQL
SQL Lesson 8: CASE — If-Then in SQL
Use CASE to label rows (price bands, order sizes), count conditions side by side with SUM(CASE…), handle NULLs with readable labels, and build pivot-style…
Read article →SQL Lesson 7: Subqueries
SQL Lesson 7: Subqueries
Use a query inside a query: compare with an average, filter with IN and NOT IN, find the row with the maximum, query a…
Read article →SQL Lesson 6: JOINs — Combining Tables
SQL Lesson 6: JOINs — Combining Tables
Combine tables with JOIN: primary and foreign keys, INNER JOIN, table aliases, joining three tables, LEFT JOIN to find missing matches, and the duplicate-row…
Read article →SQL Lesson 5: GROUP BY and HAVING
SQL Lesson 5: GROUP BY and HAVING
Get totals per group with GROUP BY — customers per region, orders per status, sales per month — filter groups with HAVING, and know…
Read article →SQL Lesson 4: COUNT, SUM, AVG, MIN and MAX
SQL Lesson 4: COUNT, SUM, AVG, MIN and MAX
Summarise data with aggregate functions: COUNT(*) vs COUNT(column), SUM, AVG with ROUND, MIN and MAX on numbers and dates, filtering before aggregating, and how…
Read article →SQL Lesson 3: ORDER BY and LIMIT
SQL Lesson 3: ORDER BY and LIMIT
Sort SQL results with ORDER BY, ascending and descending, by several columns and by calculated values; get top-N lists with LIMIT, and understand why…
Read article →SQL Lesson 2: WHERE — Filtering Rows
SQL Lesson 2: WHERE — Filtering Rows
Filter rows in SQL with WHERE: comparison operators, AND/OR with brackets, IN, BETWEEN, LIKE with % and _, and IS NULL — the SQL…
Read article →