@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix edu: <https://knobit.org/def/> .
@prefix knobit: <https://knobit.org/id/knobit/> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix register: <https://knobit.org/id/register/> .
@prefix schema: <https://schema.org/> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .

knobit:K-630 a edu:Knobit ;
    rdfs:label "Recognises a null with a business meaning"@en ;
    dcterms:identifier "K-630" ;
    dcterms:license <https://creativecommons.org/licenses/by/4.0/> ;
    dcterms:source "Review checklist 04-physical, row 19; Karwin, Fear of the Unknown; Codd 1979 §2.3"@en ;
    skos:altLabel "Sentinel value in place of null, or null with a business meaning (physical model)"@en ;
    skos:definition "A real-looking value standing for \"unknown\" or \"not applicable\", or a null that means something specific and different in different tables. Sentinels pass every constraint and end up in totals and averages. A specific form of logical row 6 at the physical level."@en ;
    skos:prefLabel "Recognises a null with a business meaning"@en ;
    edu:actionVerb "Recognises"@en ;
    edu:appliesKnowledge knobit:K-655 ;
    edu:assessmentCriterion "Flags the deficient case and passes the acceptable one. Deficient: `account_opening_date = '1900-01-01'` when unknown; `branch_id = -1`; open-ended validity as `NULL` in one table and `9999-12-31` in another Acceptable: `NULL` for unknown. Where a value is required, one project-wide convention recorded in config (open-ended `valid_to`), and a dimension's unknown member as a labelled row that every query sees, not a magic number in a measure"@en ;
    edu:assessmentMethod "skill-tests task: Loan application physical model on Snowflake (physical design anomaly skills)"@en ;
    edu:contextFunction <https://knobit.org/def/contextFunction/resultEvaluation> ;
    edu:creationMethod <https://knobit.org/def/creationMethod/aiGenerated> ;
    edu:dependsOnKnobit knobit:K-506 ;
    edu:expectedResult "The null, its meaning, and the explicit value or column stating it"@en ;
    edu:graphRelevance <https://knobit.org/def/graphRelevance/learnerState>,
        <https://knobit.org/def/graphRelevance/taskSelection> ;
    edu:knobitType <https://knobit.org/def/knobitType/skill> ;
    edu:targetObject "null meaning something specific"@en ;
    schema:creativeWorkStatus "accepted" ;
    schema:isPartOf register:data-modelling .

edu:Knobit rdfs:label "Knobit"@en,
        "Knobit"@et .

knobit:K-506 rdfs:label "Recognises an attribute with several meanings"@en .

knobit:K-655 rdfs:label "Explains null semantics and three-valued logic"@en .