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avoid data redundancy, insertion, update & deletion anomaly

Functional dependency

  • Multivalued
  • Trivial
  • Non-Trivial
  • Transitive

Normal forms in SQL

  • 1NF - unique records, table cell 1 value
  • 2NF - primary key deos not depend on subset of cadidate key
  • 3NF - not transitive dependency
  • BCNF (Boyce-Codd Normal Form)
  • A relation is in BCNF, if and only if, every determinant is a Form (BCNF) candidate key.
  • A relation is in BCNF iff, X is superkey for every functional dependency (FD) X?Y in given relation.
  • 4NF - NO (two or more, independent and multivalued data describing the relevant entity)
  • 5NF - it cannot be decomposed into any number of smaller tables without loss of data
  • 6NF - no standard yet