顶层2NF的例子不合适。
3358 en.Wikipedia.org/wiki/second _ normal _ form
notall2nftablesarefreefromupdateanomalies，however.anexampleofa2nftablewhichsuffersfromupdateanomaliesis 3360
tournamentwinnerstournamentyearwinnerwinnerdateofbirth
dsmoinesmasters 1998 chipmasterson 14 March 1977
Indiana invitational 1998 Alfred rickson 21ju ly 1975
Cleveland open 1999 bob albertson 28 September 1968
des Moines masters 1999 Alfred rickson 21ju ly 1975
Indiana invitational 1999 chipmasterson 14 March 1977
eventhoughwinnerandwinnerdateofbirtharedeterminedbythewholekey { tournament/year } andnotpartofit、 particular Winner/winnerdateofbirthcombinationsareshownredundantlyonmultiplerecords.thisleadstoanupdateanomaly 3360 ifupdatesarenotcarrriedoutcoutcoood
theunderlyingproblemisthetransitivedependencytowhichthewinnerdateofbirthattributeissubject.winnerdateofbirthactuallydepependsosorthacthacttilydesodesondesoreson
thisproblemisaddressedbythirdnormalform (3nf )。