A designer gives each applicant an auto-generated ApplicantID as the primary key, and stores the national ID number as a separate unique column. Why use this surrogate key?
Un concepteur attribue à chaque candidat un IDCandidat généré automatiquement comme clé primaire, et stocke le numéro d'identité nationale dans une colonne unique séparée. Pourquoi utiliser cette clé de substitution ?
Answers
AIt never changes and is compact, unlike real-world identifiersElle ne change jamais et reste compacte, contrairement aux identifiants du monde réel
BNational ID numbers are always far too short to be used as keys in any databaseLes numéros d'identité nationale sont toujours bien trop courts pour servir de clés dans une base
CSurrogate keys make the table encryptedLes clés de substitution chiffrent la table
DIt removes the need for any other constraintsElle supprime le besoin de toute autre contrainte
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