Stage 5: Derive the logical data model
Knobit of Data modelling · K-517 · Skill
Recognises an unstable or meaningful primary key
What it means
The key can change, be reused or be unknown when the row is created, or it carries meaning that can change. Every reference to the row breaks when it does.
How it is assessed
Flags the deficient case and passes the acceptable one. Deficient: Account keyed on branch code plus sequence: a branch merger renumbers the branches and with them every key; Party keyed on name Acceptable: Account keyed on its IBAN, assigned once and never reused; Branch Identifier as a plain attribute; where no stable natural key exists, say so and record the matching rule (`LOG-005`, `LOG-020`, `LOG-021`, `LOG-027`)
Builds on
- Explains natural keys, surrogate keys and key stabilityK-568 · Knowledge