9. A relational database restructuring system, having at least one relation, each said relation having a plurality of tuples, a set of attributes, a set of candidate keys and a set of non-key attributes, wherein each said tuple is managed as a two-dimensional relation for each said attribute and wherein each said relation has a candidate key serving as a set of attributes which can uniquely identify one of said tuples, comprising: first determination means for checking, with reference to values of tuples which are present in said relations, whether a first set of attributes is functionally dependent on a second set of attributes; division means for dividing a first relation into a second and a third relation by a projecting operation for a designated attribute set; second determination means for determining, from attribute sets A and B which are included in a relation and are mutually primary, whether said attribute sets A and B satisfy at least one of a first condition and a second condition, said first condition being that said attribute set A is a proper subset of said set of candidate keys and said attribute set B is a subset of a non-key attribute set serving as a subset of said set of candidate keys said second condition being that both the attribute sets A and B are proper subsets of said non-key attribute set; and means for checking whether said attribute set B is functionally dependent on said attribute set A once said second determination means has determined that said attribute sets A and B satisfy at least one of said first condition and said second condition, and dividing said relation including said attribute sets A and B, when said attribute set A is functionally dependent on attribute set B, into a relation formed by a projection to a subset of the attribute set B and, a relation formed by a projection to a union between said attribute sets A and B.
9. A relational database restructuring system, having at least one relation, each said relation having a plurality of tuples, a set of attributes, a set of candidate keys and a set of non-key attributes, wherein each said tuple is managed as a two-dimensional relation for each said attribute and wherein each said relation has a candidate key serving as a set of attributes which can uniquely identify one of said tuples, comprising: first determination means for checking, with reference to values of tuples which are present in said relations, whether a first set of attributes is functionally dependent on a second set of attributes; division means for dividing a first relation into a second and a third relation by a projecting operation for a designated attribute set; second determination means for determining, from attribute sets A and B which are included in a relation and are mutually primary, whether said attribute sets A and B satisfy at least one of a first condition and a second condition, said first condition being that said attribute set A is a proper subset of said set of candidate keys and said attribute set B is a subset of a non-key attribute set serving as a subset of said set of candidate keys said second condition being that both the attribute sets A and B are proper subsets of said non-key attribute set; and means for checking whether said attribute set B is functionally dependent on said attribute set A once said second determination means has determined that said attribute sets A and B satisfy at least one of said first condition and said second condition, and dividing said relation including said attribute sets A and B, when said attribute set A is functionally dependent on attribute set B, into a relation formed by a projection to a subset of the attribute set B and, a relation formed by a projection to a union between said attribute sets A and B. 12. A system according to claim 9, wherein said system further comprises means for detecting a predetermined character of attributes of said relation of said relational database, means for informing said terminal by said view means of said detection and inputting an instruction from said terminal, means for converting a non-normal relation into first normal form in accordance with said input instruction and means for converting, when a relation of said relational database has a non-normal form, said non-normal form into a first normal form in accordance with said input instruction.