Computer Knowledge

Database Management Systems

5,344 Questions

Database Management Systems (DBMS) form the core framework for data storage, retrieval, and security in modern software applications. Concepts such as the E-R model, backup planning, SQL integration, and big data architecture are essential for computer knowledge sections. This hub offers a comprehensive set of practice questions to master DBMS fundamentals and advanced database operations.

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Database Management Systems Questions

Multiple choice

What does the parameter Initial Catalog denote inside a Connection String?

  1. Database name

  2. Username

  3. Driver Name

  4. Name of RDBMS Application

  5. Project Name
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The initial catalog parameter denotes the name of the database to which we want to connect. For example, in the connection string given below, Sample is the name of the database. Data Source=servername;Intial Catalog=Sample;Integrated Security=true

Multiple choice

Consider the following relational schemes for a library database: Book Title, Author, Catalog_ no, Publisher, Year, Pr ice Collection Title, Author, Catalog_ no within the functional dependencies: I. Title Author $\rightarrow$ Catalog_no II. Catalog_no $\rightarrow$ Title Author Publisher Year III. Publisher Title Year $\rightarrow$ Pr ice

Assume {Author, Title} is the key for both schemes. Which of the following statements is true?

  1. Both Book and Collection are in BCNF

  2. Both Book and Collection are in 3NF only

  3. Book is in 2NF and Collection is in 3NF

  4. Both Book and Collection are in 2NF only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Multiple choice

Which of the following statements are TRUE?

I. The context diagram should depict the system as a single bubble. II. External entities should be identified clearly at all levels of DFDs. III. Control information should not be represented in a DFD. IV. A data store can be connected either to another data store or to an external entity.

  1. II and III

  2. II and I

  3. I and III

  4. I, II and III
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In Data Flow Diagrams (DFDs), Statement I is true because a context diagram represents the entire system as a single process bubble with external entities around it. Statement III is true because DFDs are designed to show only data flow and transformations, not control information like loops or decisions - those belong in flowcharts. Statement II is false because external entities should only appear in the context diagram and Level 1 DFD, not at all levels. Statement IV is false because data stores can only connect to processes, not directly to other data stores or external entities.

Multiple choice

Consider the following relational schema:

Suppliers(sid:integer, sname:string, city:string, street:string) Parts(pid:integer, pname:string, color:string) Catalog(sid:integer, pid:integer, cost:real) Assume that in the suppliers relation above, each supplier and each street within a city has a unique name, and (sname, city) forms a candidate key. No other functional dependency is implied other than those implied by primary and candidate keys.

Which of the following statements is TRUE about the above schema?

  1. The schema is in BCNF.

  2. The schema is in 3NF, but not in BCNF.

  3. The schema is in 2NF, but not in 3NF.

  4. The schema is not in 2NF.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 The schema is in 3NF, but not in BCNF. (sname, city) forms the candidate key.
Suppliers(sid, sname, city, street)
sname is primary key.
sid, sname is also key.
city--> street
street is functionally dependent upon city.
sname--> city
So, transitivity occurs.
So, the schema is in 3NF, but not in BCNF.

Multiple choice

Which of the following statements is incorrect about 'Repository' pattern?

  1. This pattern virtualises storage of entities in a persistent medium.

  2. It uses encapsulation technique to store the data.

  3. It allows the use of a common set of methods in the application.

  4. Its instance lifetime is that of the application domain.

  5. The repository uses a series of providers to connect to the source data.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There is no instance creation in this pattern and the instance creation is performed in Singleton pattern.

Multiple choice

An index is clustered, if

  1. it is on a set of fields that form a candidate key

  2. it is on a set of fields that include the primary key

  3. the data records of the file are organised in the same order as the data entries of the index

  4. the data records of the file are organised not in the same order as the data entries of the index
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Clustered index is built on ordering non-key field and hence, if the index is clustered, then the data records of the file are organised in the same order as the data entries of the index.

Multiple choice

Consider three data items D1, D2 and D3, and the following execution schedule of transactions T1, T2 and T3. In the diagram, R(D) and W(D) denote the actions reading and writing in the data item D respectively.

Which of the following statements is correct?

  1. The schedule is serialisable as T2; T3; T1.

  2. The schedule is serialisable as T2; T1; T3.

  3. The schedule is serialisable as T3; T2; T1.

  4. The schedule is not serialisable.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Multiple choice

Which of the following scenarios may leave the transaction vulnerable to dirty reads, phantom reads, etc. in a database system?

  1. A transaction writes a data item after it is read by an uncommitted transaction.

  2. A transaction reads a data item after it is read by an uncommitted transaction.

  3. A transaction reads a data item after it is written by a committed transaction.

  4. A transaction reads a data item after it is written by an uncommitted transaction.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 This may leave the transactions vulnerable to dirty reads, phantom reads, etc. in the database system.

Multiple choice

Consider the following log sequence of two transactions on a bank account, with initial balance of Rs. 12,000, that transfers 2000 to a mortgage payment and then applies a 5% interest.

  1. T1 start
  2. T1 B old = 1200 new = 10000
  3. T1 M old = 0 new = 2000
  4. T1 commit
  5. T2 start
  6. T2 B old = 10000 new = 10500
  7. T2 commit

Suppose the database system crashes just before log record 7 is written. When the system is restarted, which statement is true for the recovery procedure?

  1. We must redo log record 6 to set B to 10500.

  2. We must undo log record 6 to set B to 10000 and then redo log records 2 and 3.

  3. We need not redo log records 2 and 3 because transaction T1 has committed.

  4. We can apply redo and undo operations in arbitrary order because they are idempotent.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Multiple choice

Consider the following relational schemes for a library database: Book Title, Author, Catalog_ no, Publisher, Year, Pr ice Collection Title, Author, Catalog_ no within the functional dependencies: I. Title Author $\rightarrow$ Catalog_no II. Catalog_no $\rightarrow$ Title Author Publisher Year III. Publisher Title Year $\rightarrow$ Pr ice

Assume {Author, Title} is the key for both schemes. Which of the following statements is true?

  1. Both Book and Collection are in BCNF

  2. Both Book and Collection are in 3NF only

  3. Book is in 2NF and Collection is in 3NF

  4. Both Book and Collection are in 2NF only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Multiple choice

Consider the following relational schema:

Suppliers(sid:integer, sname:string, city:string, street:string) Parts(pid:integer, pname:string, color:string) Catalog(sid:integer, pid:integer, cost:real) Assume that in the suppliers relation above, each supplier and each street within a city has a unique name, and (sname, city) forms a candidate key. No other functional dependency is implied other than those implied by primary and candidate keys.

Which of the following statements is TRUE about the above schema?

  1. The schema is in BCNF.

  2. The schema is in 3NF, but not in BCNF.

  3. The schema is in 2NF, but not in 3NF.

  4. The schema is not in 2NF.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 The schema is in 3NF, but not in BCNF. (sname, city) forms the candidate key.
Suppliers(sid, sname, city, street)
sname is primary key.
sid, sname is also key.
city--> street
street is functionally dependent upon city.
sname--> city
So, transitivity occurs.
So, the schema is in 3NF, but not in BCNF.