Knobit of Data modelling · K-611 · Skill

Recognises a surrogate value with meaning, reused or renumbered

What it means

A surrogate key whose value is shown to people, built from business data, reused after a delete, or renumbered to close gaps. Every reference held outside the table, in a file, a report or a letter, then points at the wrong row. Codd's surrogates are never shown to users and never controlled by them. A specific form of logical row 17.

How it is assessed

Flags the deficient case and passes the acceptable one. Deficient: `account_id` printed on customer letters and renumbered after a purge; `loan_key` built as date plus sequence Acceptable: Identity or sequence values never reused, never displayed and with gaps accepted; the number customers see is a separate natural-key column with its own unique constraint

Builds on

Recognises an unstable or meaningful primary keyK-517 · Skill
Explains natural keys, surrogate keys and key stabilityK-568 · Knowledge
Explains persistent identifiersK-160 · Knowledge

Needed by

None