Knobit of Data modelling · K-617 · Skill

Recognises a physical domain differing from the logical domain

What it means

A datatype, length, scale, character set or nullability that admits values the logical domain forbids, or cuts off values it allows. Includes a foreign key typed differently from the key it references.

How it is assessed

Flags the deficient case and passes the acceptable one. Deficient: `account_currency_code VARCHAR(50)`: `'EUR'`, `'eur'` and `'EUR '` all load. `account_identifier VARCHAR(10)` for a logical length of 20. `payment.account_id INTEGER` referencing `BIGINT`. A date as `VARCHAR`. A name column in a character set that cannot hold õ, ä, ö, ü, š, ž Acceptable: `CHAR(3)` with an uppercase-letters check; lengths at least the logical ones; foreign-key types identical to the referenced key; `DATE`; a Unicode character set (`PHY-008`, `PHY-023`)

Builds on

Explains attribute domainsK-562 · Knowledge

Needed by

Recognises one decimal scale for every currencyK-816 · Skill
Recognises a length taken from sample dataK-817 · Skill
Recognises an event timestamp stored without a time zoneK-827 · Skill
Recognises a business date stored with a time of dayK-828 · Skill