Stage 6: Design the physical data model
Knobit of Data modelling · K-601 · Skill
Recognises an unmanaged duplicate column
What it means
A column copied from another table to save a join, with nothing keeping the copy equal to the original. The update anomaly the logical model removed, put back.
How it is assessed
Flags the deficient case and passes the acceptable one. Deficient: `account.holder_name` copied from `party.name` for the account-servicing screen, no `derivation`, no DQ rule; the holder changes name and old accounts show the old one Acceptable: `derivation` names the source column and the mechanism that refreshes it, and a `consistency` DQ rule compares the two; or a view instead of a column. A copy meant to keep the value as at account opening is not a copy: the logical model says so (logical row 9)
Builds on
- Recognises an update anomaly in a logical data modelK-502 · Skill
- Explains controlled denormalisationK-651 · Knowledge
- Explains derived data and point-in-time snapshotsK-565 · Knowledge