?????????У???????????????????й??????????????????????????????????????
???????????????壺????????R?е????з?????????κκ????????????????????????????R???????????????????R 3NF??
?????磺????????S1???????????????????????????
??????????????????????????????????????????????????????????????????????—>???????—>???????—>?????????????—>???? ????????????????????????????“???”?????????????????????“????”?????????????????????????????????
????SC????????????????
????D?????????????????
????C???γ????γ?????????
????S???????γ????????
??????????“??????”???????????????????????????????????????????????????????????м?“????”????????????????????????????????????????????????????????????????
????BCNF????壺?????????R?е??????????????????????R???κκ????????????????R?е???????????????????????????????R????BCNF?????????R BCNF??
???????????BCNF????????
????1.???з?????????????????????????????
????2.???е????????????????????????????????????????
????3.????κ???????????????????????κ?????????
????????RBCNF??????????????κ??????????????????????????????R3NF????????R3NF????Rδ??????BCNF??
?????????ü??????????????3NF???????е?????BCNF?????е??????BCNF??
??????????...
??????l ?????SJP(S??J??P)?У?S???????J????γ??P??????Ρ??????????????γ??????????????Σ????γ????????????????????????в??????Σ??????????????????????????
????(S??J)→P ??(J??P)→S
????????(S??J)??(J??P)???????????????????????????????????????????????????????????????????????????????????????????????SJP3NF???????(S??J)??(J??P)????????????????????????SJPBCNF??
??????2 ?????STJ(S??T??J)?У?S????????T????????J????γ?????????????Ρ?????????????????????????Σ????????????????????????????μ??????????
????(S??J)→T??(S??T)→J??T→J??
????????(S??J)??(S??T)????????
????STJ??3NF?????????κη????????????????????????????STJ????BCNF????????T????????????T????????
????3NF??“??????”???????????????????????????????????????????BCNF???????????????????BCNF??????STJ?????ST(S??T)??TJ??T??J)?????????BCNF??
??????????е??????????????BCNF??????????????????????????????????????????????????????????
??????????淶??С??
?????????淶??????????????????????洢???????????????С??????????????????
????????????????“??????”????????????????????????????????????????淶???????????????
????????????????????????????????????????????
???????????????????????????????“???”????????????????????????????????????????????????????????