Question

DBMS class

funcbonal U in & set tion of the principle of closure ot of tunca te key(s) of a relation schen a set of functional superkey n attribute at a time from K unt K ence rules for of an attribute uses a It is possible to progressively dencies through the systematic ond method for identitying the candida l dependencies that prevai hat of decomposition. In this method. given Universal Relation Schema (URS), the superkey, K, consisting of a gressively decomposed by arbitrarily that is not further reducible (i.e, no MPL removing nederstrddae quenes vielding a candidate key. The other candidate keys of URS are derivedt candidate key by the application of the pseudotransitivity rule igFa eiamples are used to illustrate the use of Amstrong's axioms to derive s axiom the and 7 8 candidate kehtee chema using the method of synthesis and the method of d of prime/non-prime Finaly de et of thumb to choose and key/non-key attributes are presented, alo a primary key from among the candidate keys dl a with a handful of Exercises 1. What is the purpose of the normalization technique in the data modeling on in the STOCK 9 10 71 2. Explain why data redundancy exists for the attributes Discount and Location io table in Figure 7.1c. 3. Explain functional 4. Why can functiona dependency between two attributes I dependency not be inferred from a particular relation state?

Answer 1

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1.Purpose of normalisation:

The purpose of normalisation technique is to reduce redundancy and to remove un-necessary attributes from the tables which will ultimately leads us to the optimised data table.

2.Why Redundancy exists:

There may be a chance that two tables may have some common attributes which leads us to redundancy,having same attribute in different tables has no use, so redundancy may occur.

3.Functional dependency between two attributes:

If the two attributes are linked by the or derived by the same property then they may be said as function dependency occurs between them.

4.Functional dependency cannot be inferred:

Functional dependencies cannot be inferrd from one state because the two states may have different attributes which causes impossible to infer functional dependencies.