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41. The relational model consists of:
a. data in the form of tables.
b. data redundancy.
c. operations using non-SQL languages.
d. unorganized data.
Answer: (a).data in the form of tables.

42. A primary key is which of the following?
a. Any attribute
b. An attribute that uniquely identifies each row
c. An attribute that uniquely identifies each column
d. A derived attribute
Answer: (b).An attribute that uniquely identifies each row

43. A foreign key is which of the following?
a. Any attribute
b. The same thing as a primary key
c. An attribute that serves as the primary key of another relation
d. None of the above.
Answer: (c).An attribute that serves as the primary key of another relation

44. Relations are:
a. two-dimensional tables.
b. three-dimensional tables.
c. four-dimensional tables.
d. five-dimensional tables.
Answer: (a).two-dimensional tables.

45. A relation has which of the following properties?
a. Each row is not unique.
b. Attributes can have the same name within a given table.
c. Each relation has a unique name.
d. The order of the columns is significant.
Answer: (c).Each relation has a unique name.

46. The entity integrity rule states that:
a. no primary key attribute may be null.
b. no primary key can be composite.
c. no primary key may be unique.
d. no primary key may be equal to a value in a foreign key.
Answer: (a).no primary key attribute may be null.

47. When mapping a multivalued attribute into a relation which of the following is true?
a. One relation is created.
b. Two relations are created.
c. Three relations are created.
d. Four relations are created.
Answer: (b).Two relations are created.

48. When mapping a regular entity into a relation which of the following is true?
a. One relation is created.
b. Two relations are created.
c. Three relations are created.
d. Four relations are created.
Answer: (a).One relation is created.

49. When mapping a binary many-to-many relationship into a relation which of the following is true?
a. One relation is created.
b. Two relations are created.
c. Three relations are created.
d. Four relations are created.
Answer: (c).Three relations are created.

50. When mapping a many-to-many unary relationship into a relation which of the following is true?
a. One relation is created.
b. Two relations are created.
c. Three relations are created.
d. Four relations are created.
Answer: (b).Two relations are created.

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