test series

Question

May anyone please provide an explanation? 

Comments

join of different decomposition would have more or same no. of tuples as in old relation...

let a relation R has two decomposition  r1 and r2

case1 :-there is a common attributes :-then join operation will include all the tuples presented in R...

case2.:no common attributes then join operation will behave like cross product and result will lead to M*N(M in r1 and N in r2) tuples i.e >= no. of tuples in R

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join are always of two types viz. lossless or lossy.

CASE 1: lossy, then r1⋈r2⋈...rn $\supset$ u

CASE 2: lossless, then r1⋈r2⋈...rn = u.

combining both, r1⋈r2⋈...rn $\supseteq$ u