1. A data model consists of the following except a. data b. structure of data op
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Question
1. A data model consists of the following except a. data b. structure of data operations on data constraints on data c. d. 2. The relational model is based on a. binary trees b. well-formed tagged texts C. two-dimensional tables. d. UML subclasses 3. Each tuple in a relation has one component for each attribute of the relation row of the relation domain of the relation schema of the relation a. c. b. d. 4. An instance of a relation is a. b. c. d. a subset of attributes of the relation a set of tuples of the relation. a name of the relation a domain of the relation 5. Which relational algebra operation does not affect the tuples of a relation? a. union b. selection c. join d. renaming The maximum number of tuples in the Cartesian product of two relations with m and n tuples, respectively, is 6. a. m + n C. m b. mn d. m log n 7· 0color-red (Socks) = (the empty set) is a constraint to the relation Socks stating that Some socks may be red Some socks shall not be red All socks shall be red c. d. a. b. No sock may be red 8. The domain of the only common attribute of two relations consists only two values. The natural join of these two relations will have only two tuples at most two tuples at most four tuples possibly more than four tuples a. c. b. d.Explanation / Answer
1. a
The data model only describes the way data is stored and accessed. It does not contain any data.
2. c
A relational model is based on rows and columns. Columns are the attributes and the rows are the tuples. A table is called a relation.
3. a
4. b
5. d
6. b
7. b
8. d
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