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If $D_1,D_2, \dots D_n$ are domains in a relational model, then the relation is a table, which is a subset of

  1. $D_1 \oplus D_2 \oplus \dots \oplus D_n$
  2. $D_1 \times D_2 \times \dots \times D_n$
  3. $D_1 \cup D_2 \cup \dots \cup D_n$
  4. $D_1 \cap D_2 \cap \dots \cap D_n$
in Databases by Junior (945 points) | 2.7k views
0
i didd not get this question
0
does domain means - "Set of all possible values for a Field / attribute" ? or something else

2 Answers

+12 votes

yes option B is correct .because a relation can be utmost D1XD2X....XDn

by Boss (14.4k points)
0
yup thx...
0 votes

Given sets $D_{1}, \  D_{2}, \  …, \  D_{n} $ not necessarily distinct.

The Cartesian product $D_{1}XD_{2}X.....XD_{n}$ is the set of all (ordered) $n-tuples$  $< d_{1}, \ d_{2}, \ d_{3}, \ ....... \, \ d_{n} >$   such that $d_{1} \ \epsilon \ D_{1} , \ d_{2} \ \epsilon \ D_{2} \ ..........., \ d_{n} \ \epsilon \ D_{n}$

A mathematical relation on $D_{1}, \  D_{2}, \  …, \  D_{n} $ is a subset of the Cartesian product $D_{1}XD_{2}X.....XD_{n}$

$D_{1}, \  D_{2}, \  …, \  D_{n} $ are the domains of the relations.

by Boss (10.8k points)
Answer:

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