DBMS - relational calculus and entity relationship model

Find the ID, name, dept name, salary for instructors whose salary is greater than $80,000 .

• {t | t ε instructor ∧ t[salary] > 80000}

• Э t ∈ r (Q(t))

• {t | Э s ε instructor (t[ID] = s[ID]∧ s[salary] > 80000)}

• None of the mentioned

A query in the tuple relational calculus is expressed as:

• {t | P() | t}

• {P(t) | t }

• {t | P(t)}

• All of the mentioned

An expression in the domain relational calculus is of the form

• {P(x1, x2, . . . , xn) | < x1, x2, . . . , xn > }

• {x1, x2, . . . , xn | < x1, x2, . . . , xn > }

• { x1, x2, . . . , xn | x1, x2, . . . , xn}

• {< x1, x2, . . . , xn > | P(x1, x2, . . . , xn)}

An ________ is a set of entities of the same type that share the same properties, or attributes.

• Entity set

• Attribute set

• Relation se

• Entity model

Entity is a _________

• Object of relation

• Present working model

• Thing in real world

• Model of relation

The function that an entity plays in a relationship is called that entity’s _____________

• Participation

• Position

• Role

• Instance

The attribute name could be structured as an attribute consisting of first name, middle initial, and last name. This type of attribute is called _______________

• Simple attribute

• Composite attribute

• Multivalued attribute

• Derived attribute

Which of the following can be a multivalued attribute?

• Phone_number

• Name

• Date_of_birth

• All of the mentioned

Which of the following is a single valued attribute

• Register_number

• Address

• SUBJECT_TAKEN

• Reference

In a relation between the entities the type and condition of the relation should be specified. That is called as______attribute.

• Desciptive

• Derived

• Recursive

• Relative