Home › GATE CSE › computerscience › Database Management Systems › An FD `pincode → city` is best justified by
An FD `pincode → city` is best justified by
Athe meaning of pincodes (each pincode names exactly one city, by India Post design)
Bno two rows in today's small snapshot disagreeing on city for the same pincode
Cthe database engine inferring it from the index
Dthe (pincode, city) pair appearing on every form
Answer & Solution
Correct answer: A. the meaning of pincodes (each pincode names exactly one city, by India Post design)
An FD is a rule about every possible state, not a coincidence in one snapshot. Today's data might look consistent and tomorrow's might not. Only the meaning of the attribute (pincodes name unique cities by post-office design) gives the rule force. Snapshots can mislead; engines do not infer FDs.
Related questions
The main reasons production DBMSs avoid shadow paging in favour of WAL are that shadow pagWhat is the purpose of a Compensation Log Record (CLR) in ARIES?ARIES recovery is structured as exactlyFuzzy checkpoints differ from naive checkpoints byIn standard log-based recovery, the order of operations isAfter a crash, with checkpointing, the recovery system scans the logA complete log record for a write operation includesPer WAL semantics, a transaction is officially committed at the moment