DBMS 面试题与答案
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问题 41. What is degree of a Relation?
It is the number of attribute of its relation schema.
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问题 42. What is Relationship?
It is an association among two or more entities.
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问题 43. What is Functional Dependency?
A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.
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问题 44. What is 1 NF (Normal Form)?
The domain of attribute must include only atomic (simple, indivisible) values.
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问题 45. What is Fully Functional dependency?
It is based on concept of full functional dependency. A functional dependency X Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.
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