说明：  关系的定义： D1×D2×…×Dn 的子集叫作在域D1，D2，…，Dn上的关系，表示为R（ D1，D2，…，Dn） 其中 R :关系的名字 D i :第i个域名（属性） n :关系的目或度
(The normalization theory is used to transform the relational model, and to eliminate the inappropriate data dependency by decomposing the relational model, so as to solve the problems of insertion exception, deletion exception, update exception and data redundancy)