Second Normal Form Definition

• Each non-key column must depend on the entire key.

  • Only applies to concatenated keys
  • Some columns only depend on part of the key
  • Split those into a new table.

• Dependence (definition)

  • If given a value for the key you always know the value of the property in question, then that property is said to depend on the key.
  • If you change part of a key and the questionable property does not change, then the table is not in 2NF.

RentalLine(TransID, VideoID, Copy#, Title, Rent)

Depend only on VideoID

Depends on both TransID and VideoID

前一張投影片

下一張投影片

回到第一張投影片

檢視圖形版本