A                  on an attribute of a relation is a data structure that allows the database system to find those tuples in the relation that have a specified value for that attribute efficiently, without scanning through all the tuples of the relation.

Related MCQs

• Which one of the following provides the ability to query information from the database and to insert tuples into, delete tuples from, and modify tuples in the database?
• Database __________ which is the logical design of the database, and the database _______ which is a snapshot of the data in the database at a given instant in time.
• Database __________ , which is the logical design of the database, and the database _______,which is a snapshot of the data in the database at a given instant in time.
• Suppose now that R(A,B:) and S(A,B:) are two relations with r and s tuples, respectively (again, not necessarily distinct). If m is the number of (not necessarily distinct) tuples in the result of the SQL query: R intersect S; Then which of the following is the most restrictive, correct condition on the value of m?
• Every time attribute A appears, it is matched with the same value of attribute B, but not the same value of attribute C. Therefore, it is true that:
• An attribute in a relation is a foreign key if the                key from one relation is used as an attribute in that relation.
• The relation with the attribute which is the primary key is referenced in another relation. The relation which has the attribute as a primary key is called                              
• An attribute in a relation is a foreign key if the _______ key from one relation is used as an attribute in that relation.
• The relation with the attribute which is the primary key is referenced in another relation. The relation which has the attribute as a primary key is called ______________
• A attribute in a relation is a foreign key if the _______ key from one relation is used as an attribute in that relation .