04 Try it yourself Interactive
The same five enrolments as section 02, in two runs. Decompose starts one step earlier than section 02 — at the unflattened table — then walks UNF to 3NF, moving one column group per step and showing repeated cells fall to zero. Anomalies stays on the denormalised table and performs the three operations that go wrong. Every press of Next moves the tables and the narration; the highlighted line of the plan advances each time a new rule comes into play, so a single line usually spans two steps — the setup and its consequence.