范式图形辨析
首先用一句话总结要辨析的5中范式分别解决的问题： 1NF：属性原子性 2NF:部分依赖 3NF：传递依赖（非主属性对关键码） BCNF：传递依赖（主属性对候选键） 4NF：（最高级别的范式，不常用这里引用定义）D是R上成立的FD和MVD集合，并且D中每个非平法的X→→Y的
首先用一句话总结要辨析的5中范式分别解决的问题：
1NF：属性原子性
2NF:部分依赖
3NF：传递依赖（非主属性对关键码）
BCNF：传递依赖（主属性对候选键）
4NF：（最高级别的范式，不常用这里引用定义）D是R上成立的FD和MVD集合，并且D中每个非平法的X→→Y的左部X都是R的超键
其中第一范式，画图省略。第四范式不常用画图省略。
2NF如下：
3NF:
BCNF：喎?http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">vcD4KPHA+PGltZyBzcmM9"http://www.2cto.com/uploadfile/Collfiles/20141022/2014102209204921.jpg" alt="\">
至于4NF，我现在还不是太清楚，请大侠指教。但是其他的范式，我自我感觉理解还可以，若有不懂的朋友可以点击右上角的“Q我吧”一起探讨~
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