Recognises nulls left to chance in a check predicate
https://knobit.org/id/knobit/Q-314
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| Context functions | Result evaluation |
|---|---|
| Knobit creation methods | AI generated, human edited |
| Knobit types | Skill |
| LCG purposes | Assessing the learner's knowledge or skill state |
| LCG purposes | Selecting an assessment task or learning activity |
| action verb | Recognises en |
| applies knowledge | Explains null semantics and three-valued logic |
| assessment criterion | Flags the deficient case and passes the acceptable one. Deficient: Copied from the CHECK: `interest_rate_type_code IN ('FIX','VAR')` on an optional column — every current account with no rate type fails. Or `WHERE account_currency_code NOT IN (SELECT currency_code FROM ref_currency)` with one null code in the reference table: no violation ever found Acceptable: `interest_rate_type_code IS NULL OR interest_rate_type_code IN (...)` where null is allowed, and a separate completeness check where it is not; `NOT EXISTS` instead of `NOT IN` en |
| assessment method | skill-tests task: Loan application data quality rules on Snowflake (DQ rule anomaly skills) en |
| conforms to profile | https://oppekava.edu.ee/a/Knobitite_kirjeldamise_ja_seostamise_reeglid#LCG-KNOBIT-0.1 |
| dcterms:identifier | Q-314 |
| dcterms:license | https://creativecommons.org/licenses/by/4.0/ |
| dcterms:source | Review checklist 03-dq-rules (data-quality), row 14; ISO 9075; Codd 1979; formerly data-modelling K-714 en |
| expected result | The predicate and the explicit null decision en |
| owl:sameAs | https://bitbucket.org/reffa/ontology/id/knobit/data-modelling/07-dq-rules/14 |
| rdfs:label | Recognises nulls left to chance in a check predicate en |
| schema:creativeWorkStatus | accepted |
| schema:isPartOf | Data quality management (DAMA-DMBOK2) |
| skos:altLabel | Nulls treated by accident (data quality rule) en |
| skos:definition | A predicate that evaluates to `UNKNOWN` for nulls, where nobody decided whether a null passes. A `CHECK` passes `UNKNOWN`; a DQ row predicate fails it; a violation query written as `WHERE NOT (expr)` silently drops it. And `NOT IN` against a subquery that returns a null matches nothing. en |
| skos:prefLabel | Recognises nulls left to chance in a check predicate en |
| target object | predicate evaluating to UNKNOWN en |
Used by
| includes knobit | Derives data quality rules from the data rules and the physical model |
|---|---|
| includes knobit | Develop and deploy data quality operations: manage data quality rules |
| requires knobit | Derive data quality rules |