DBMS Unit 3 Part 3 Database Design & Normalization

Explain with suitable illustration how functional dependences can be used to show that decay are lossless. AKTU 2015- 16, Marks 10 Answer Functional reliance ReferQ. Rn} of a relation R is called a lossless corruption for R if the natural join of R1, R2,. Following are the condition to show that decay are lossless using FD set 1.

Union of attributes of R1 and R2 must be equal to trait ofR. Each trait of R must be either in R1 or in R2. Common trait must be a key for at least one relation Att Att Att or Att Att Att For illustration Consider a relation R with FD set A BC and A D is perished into R1 and R2 which is a lossless join corruption as 1. Consider the relation r the set F = { X Z, Y Z, Z W, WQ Z, ZQ X} and the corruption of r into relations R1, R2, R3, R4 and R5.

Check whether the decay are lossy or lossless. Answer To check the corruption is lossless following condition should hold. R5 = = X Q = Since, condition 2 violates the condition of lossless join corruption. Hence corruption is lossy.

After relating the data objects of the proposed database, their connections define the tables required and columns within each table. The abecedarian principle of normalization is, « The same data should not be stored in multiple places. » It helps to remove the redundancy from the relation. It helps in easy manipulation of data.

Answer Multivalued reliance 1. MVD occurs when two or further independent multivalued data about the same trait do within the same relation. MVD is denoted by X Y specified on relation schema R, where X and Y are both subsets ofR. A Join reliance, denoted by specified on relation scheme R, specifies a constraints on the countries r ofR.

The constraint states that every legal state r of R should have a lossless join corruption into R1, R2,. A join reliance JD, specified on relation schema R, is a trivial JD if one of the relation schemas Ri in JD is equal toR. Such a reliance is called trivial because it has the lossless join property for any relation state r of R and hence doesn’t specify any constraint onR. Given relation R with the functional dependences F = { AB CD, A E, C D}, the corruption of R into R1, R2, R3 check whether the relation is lossy or lossless.

Answer trait preservation condition on corruption 1. The relational database design algorithms start from a single universal relation schema R = { A1, A2,. , An} that includes all the attributes of the database. We implicitly make the universal relation supposition, which states that every trait name is unique.

Using the functional dependences , the algorithms putrefy the universal relation schema R into a set of relation schemas D = { R1, R2,. After applying first two functional dependences first row contain all « a » symbols. Hence it’s lossless join. OR Describe hanging tuples.

Answer An alternate approach to database design is swinging tuples 1. Tuples that « vanish » in calculating a join are known as hanging tuples. A tuple t of relation Ri is a hanging tuple if t isn’t in the relation Ri 2. The relation r1 r2.

rn is called a universal relation since it involves all the attributes in the « macrocosm » defined by R1 R2. still, rather of putrefying a If hanging tuples are allowed in the database. universal relation, we may prefer to synthesize a.

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