Reasoning About FDs (Contd.)

• Couple of additional rules (that follow from AA):

  • Union: If X Y and X Z, then X YZ
  • Decomposition: If X YZ, then X Y and X Z

• Example: Contracts(cid,sid,jid,did,pid,qty,value), and:

  • C is the key: C CSJDPQV
  • Project purchases each part using single contract: JP C
  • Dept purchases at most one part from a supplier: SD P

• JP C, C CSJDPQV imply JP CSJDPQV

• SD P implies SDJ JP

• SDJ JP, JP CSJDPQV imply SDJ CSJDPQV

Previous slide

Next slide

Back to first slide

View graphic version