1.2.12. Referential integrity

  • Given two relations R1 and R2
    • R1 contains a foreign key (FK) that references
    • A primary key (PK) in R2
      • R1 referencing relation, R2 referenced relation
    • Shared domains: dom(FK) = dom(PK)
    • Foreign exists: t1 in r(R1), t2 in r(R2)
      • t1[FK] = t2[PK] || NULL