Stage 1 · Lesson 1 of 8
Tables, rows and columns
A keeps data in tables. Each table holds one kind of thing, such as customers or orders. Each row is one of those things, like one customer.
Each column is one detail about it, like a name or a date, and every value in a column has the same type. Tables do not copy each other's data. Instead they point at each other with key values: an order stores customer_id 42, not the customer's name.
Because each fact is stored only once, can combine tables to answer questions nobody planned for when the database was built. Everything later in this roadmap, from joins to normalisation, builds on this picture.
Common traptreating a table like a spreadsheet tab and packing several facts into one cell, such as a comma-separated list of product names, which makes every later query harder.
A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock
Resources for this stage
Start with· follow one of these
- CourseFreeCS50's Introduction to Databases with SQL
Harvard University · Beginner
Watch Lecture 0 (Querying) for the relational model; it uses SQLite, and the ideas carry straight across
- GuideFreeMySQL Tutorial (official manual)
Oracle · Beginner
The official tutorial chapter: connecting, entering queries and creating your first database and tables