Database Paradigm Summary 1NF 2NF BCNF 3NF 4NF DB Normal form

1.1NF means that each variable in the relationship is not re-divided

2.2NF refers to a partially dependent 1NF elimination of the non-primary attribute pair code (candidate key)

For example (s#,c#), SN, (s#,c#), SD. S#->SD so the SD part depends on the candidate key, not 2NF, only can be 1NF; decomposition to SC (s#, C #, G) and S_SD (S#,sn,sd,dean) is 2NF

3. Bcnf refers to the 2NF which eliminates the partial dependence of the main attribute pair code (candidate key)

For example (s#,c#)->t#, t#->c# is not bcnf. Because candidate is (s#,t#), (s#,c#), the main attribute C # part relies on (s#,t#), so it is not bcnf. Can be decomposed into:

(s#,t#), (t#,c#) two sheets

4.3NF refers to the elimination of transfer-dependent BCNF

For example S#->SD, Sd->dean is not 3NF, because DEAN transmission relies on s#, can be decomposed into student (S#,SN,SD) and dept (Sd,dean)

4.4NF refers to the elimination of the multi-valued dependence of 3NF

Like what:

His original primary key is (c#,t#,b#), decomposed into (c#,t#) and (c#,b#)

COMMENTS:SN = Student Name, SD = Student Department, t# = the # of teacher

Database Paradigm Summary 1NF 2NF BCNF 3NF 4NF DB Normal form