Recognises a default inventing a business fact
A DEFAULT on a business column rather than a technical one. CURRENT_DATE on a value date fabricates a date when the feed omits one; 0 on an amount turns "unknown" into "zero", and the zero then sums into a total that reconciles; 'OPN' on a status decides a business state on the loader's behalf.
Can AI do this?
People still lead Few or none of the tested AI models showed they master this. 0 of 10 models master it.
| Model | Tier | Probability of mastery | Status |
|---|---|---|---|
| gemini-4-argon | Flagship | 40% | Not shown |
| gemini-3.1-pro-preview | Flagship | 40% | Not shown |
| gpt-6-astra | Flagship | 41% | Not shown |
| claude-fable-5-1 | Flagship | 39% | Not shown |
| gemini-3.8-flash | Mid tier | 38% | Not shown |
| gpt-6.1-sol | Mid tier | 39% | Not shown |
| claude-sonnet-5-5 | Mid tier | 38% | Not shown |
| gemini-3.5-flash-lite | Low cost | 40% | Not shown |
| gpt-6-luna | Low cost | 42% | Not shown |
| claude-haiku-5-5 | Low cost | 41% | Not shown |
Mastered means a probability of at least 90% that the model has this knobit, estimated from its graded answers. “Not shown” means the answers do not settle it either way. How the models are tested.
What it looks like in practice
Expected result: The default and the null or rule replacing it
How it is assessed: Flags the deficient case and passes the acceptable one. Deficient: settled_amount DECIMAL(14,2) DEFAULT 0: unsettled payments arrive as zero, the settlement total reconciles to the cent, and the missing settlements are invisible in exactly the figure someone reports Acceptable: settled_amount nullable with no default and a completeness DQ rule over the payments that should have settled. Defaults only on created_at/updated_at and on identity columns — and note the generator rejects a column that declares both identity: true and a default
Also known as: Default that invents a business fact (generated DDL)
Related knobits
Builds on
- K-629 Recognises a sentinel value standing in for null
- K-655 Explains null semantics and three-valued logic
All 33 knobits of Generate and review DDL.
Source: Review checklist 08-ddl, row 20; ISO 9075; Kimball 2013