Quick Reference: Grain, Surrogate, Degenerate, Junk, Bridge
Recall a compact set of dimensional modeling helpers and when each one is appropriate.
GRAIN What should a quick grain check cover? Use this before selecting columns. What is a surrogate key doing in a warehouse dimension? It gives the warehouse a stable internal key so history and conformance are not hostage to operational identifiers. This is especially important when source keys change, collide, or arrive late. When is a degenerate dimension appropriate? When a transaction identifier is useful for analysis but has no separate descriptive attributes worth a full dimension table. Classic examples are order number, invoice number, or ticket number on a fact row. When is a junk dimension appropriate? When several…
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