Database Management Systems-TYPICAL QUESTIONS & ANSWERS
Choose the correct or the best alternative in the following:
Q.1 Which of the following relational algebra operations do not require the participating tables to be union-compatible? (A) Union (B) Intersection (C) Difference (D) Join Ans: (D)
Q.2 Which of the following is not a property of transactions? (A) Atomicity (B) Concurrency (C) Isolation (D) Durability Ans: (B)
Q.3 Relational Algebra does not have (A) Selection operator. (B) Projection operator. (C) Aggregation operators. (D) Division operator. Ans: (C )
Q.4 Checkpoints are a part of (A) Recovery measures. (B) Security measures. (C ) Concurrency measures. (D) Authorization measures. Ans: (A)
Q.5 Tree structures are used to store data in (A) Network model. (B) Relational model. (C) Hierarchical model. (D) File based system. Ans: (C )
Q.6 The language that requires a user to specify the data to be retrieved without specifying exactly how to get it is (A) Procedural DML. (B) Non-Procedural DML. (C) Procedural DDL. (D) Non-Procedural DDL. Ans: (B)
Q.7 Precedence graphs help to find a
(A) Serializable schedule. (B) Recoverable schedule. (C) Deadlock free schedule. (D) Cascadeless schedule.
Ans: (A)
Q.8 The rule that a value of a foreign key must appear as a value of some specific table is called a
(A) Referential constraint. (B) Index. (C) Integrity constraint. (D) Functional dependency.
Ans: (A) The rule that a value of a foreign key must appear as a value of some specific table is called a referential constraint. (Referential integrity constraint is concerned with foreign key)
Q.9 The clause in SQL that specifies that the query result should be sorted in ascending or descending order based on the values of one or more columns is (A) View (B) Order by (C) Group by (D) Having
Ans: (B) The clause in SQL that specifies that the query result should be sorted in ascending or descending order based on the values of one or more columns is ORDER BY. (ORDER BY clause is used to arrange the result of the SELECT statement)
Q.10 What is a disjoint less constraint?
(A) It requires that an entity belongs to no more than one level entity set.
(B) The same entity may belong to more than one level.
(C) The database must contain an unmatched foreign key value.
(D) An entity can be joined with another entity in the same level entity set.
Ans: (A) Disjoint less constraint requires that an entity belongs to no more than one level entity set. (Disjoint less constraint means that an entity can be a member of at most one of the subclasses of the specialization.)
Q.11 According to the levels of abstraction, the schema at the intermediate level is called (A) Logical schema. (B) Physical schema. (C) Subschema. (D) Super schema. Ans: According to the levels of abstraction, the schema at the intermediate level is called conceptual schema. (Note: All the options given in the question are wrong.)
Q.12 It is an abstraction through which relationships are treated as higher level entities (A) Generalization. (B) Specialization. (C) Aggregation. (D) Inheritance. Ans: (C ) It is an abstraction through which relationships are treated as higher level entities Aggregation. (In ER diagram, aggregation is used to represent a relationship as an entity set.)
Q.13 A relation is in ____________ if an attribute of a composite key is dependent on an attribute of other composite key. (A) 2NF (B) 3NF (C) BCNF (D) 1NF Ans: (B) A relation is in 3 NF if an attribute of a composite key is dependent on an attribute of other composite key. (If an attribute of a composite key is dependent on an attribute of other composite key then the relation is not in BCNF, hence it has to be decomposed.)
Q.14 What is data integrity? (A) It is the data contained in database that is non redundant. (B) It is the data contained in database that is accurate and consistent. (C) It is the data contained in database that is secured. (D) It is the data contained in database that is shared.
Ans: (B) (Data integrity means that the data must be valid according to the given constraints. Therefore, the data is accurate and consistent.)
Q.15 What are the desirable properties of a decomposition (A) Partition constraint. (B) Dependency preservation. (C) Redundancy. (D) Security.
Ans: (B) What are the desirable properties of a decomposition – dependency preserving. (Lossless join and dependency preserving are the two goals of the decomposition.)
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