List of top Computer Science and IT Engineering Questions on Database Management Systems

If a relational decomposition is not dependency-preserving, which one of the following relational operators will be executed more frequently in order to maintain the dependencies?
Consider the following two relations, named Customer and Person, in a database:

\[ \text{Person} \left( \begin{array}{l} \text{aadhaar CHAR(12) PRIMARY KEY,} \\ \text{name VARCHAR (32);} \end{array} \right) \]

\[ \text{Customer} \left( \begin{array}{l} \text{name VARCHAR (32),} \\ \text{email VARCHAR(32) PRIMARY KEY,} \\ \text{phone CHAR(10),} \\ \text{aadhaar CHAR(12),} \\ \text{FOREIGN KEY (aadhaar) REFERENCES Person (aadhaar);} \end{array} \right) \]

Which of the following statements is/are correct?
Consider a database relation \( R \) with attributes \( A, B, C, D, E, F, G \), and having the following functional dependencies: \[ A \rightarrow BCEF \quad E \rightarrow DG \quad BC \rightarrow A \] Which of the following statements is/are correct?

Consider the following database tables of a sports league. player (\( pid \), \( pname \), \( age \)) coach (\( cid \), \( cname \)) team (\( tid \), \( tname \), \( city \), \( cid \)) members (\( pid \), \( tid \)) An instance of the table and an SQL query are given. Player table

coach table:

team table:

members table:

SQL query: \[ {SELECT MIN(P.age)} \] \[ {FROM player P} \] \[ {WHERE P.pid IN (} \] \[ { SELECT M.pid} \] \[ { FROM team T, coach C, members M} \] \[ { WHERE C.cname = 'Mark'} \] \[ { AND T.cid = C.cid} \] \[ { AND M.tid = T.tid)} \] The value returned by the given SQL query is __________. (Answer in integer)

Which one of the options given below refers to the degree (or arity) of a relation in relational database systems?
Consider the syntax-directed translation with non-terminals N, I, F, B and the rules:

\[ \begin{aligned} N &\to I\ \#\ F \qquad && N.val = I.val + F.val \\ I &\to I_1\ B \qquad && I.val = 2 \times I_1.val + B.val \\ I &\to B \qquad && I.val = B.val \\ F &\to B\ F_1 \qquad && F.val = \tfrac12 \big(B.val + F_1.val\big) \\ F &\to B \qquad && F.val = \tfrac12 B.val \\ B &\to 0 \qquad && B.val = 0 \\ B &\to 1 \qquad && B.val = 1 \end{aligned} \] Find the value computed for the input string 10#011 (rounded to three decimals).
Consider the table Student with attributes (rollNum, name, gender, marks). The primary key is rollNum. The SQL query is: 
SELECT *
FROM Student
WHERE gender = 'F' AND marks > 65;
The number of rows returned by this query is:

A database has 25,000 fixed-length records of 100 bytes (primary key 15 bytes). The data file is block-aligned so each record is fully contained within a block. The file is indexed by a primary index file, also block-aligned and ordered. Block size is 1024 bytes and a block pointer is 5 bytes. Each index entry stores the block’s anchor key (15 bytes) and a pointer (5 bytes). Binary search on an index file of \(b\) blocks needs \(\lceil \log_2 b \rceil\) block accesses in the worst case. Given a key, the number of block accesses required to identify the data file block that may contain the record, in the worst case, is ____________.

Consider the syntax-directed translation with non-terminals N, I, F, B and the rules:

\[ \begin{aligned} N &\to I\ \#\ F \qquad && N.val = I.val + F.val \\ I &\to I_1\ B \qquad && I.val = 2 \times I_1.val + B.val \\ I &\to B \qquad && I.val = B.val \\ F &\to B\ F_1 \qquad && F.val = \tfrac12 \big(B.val + F_1.val\big) \\ F &\to B \qquad && F.val = \tfrac12 B.val \\ B &\to 0 \qquad && B.val = 0 \\ B &\to 1 \qquad && B.val = 1 \end{aligned} \] Find the value computed for the input string 10#011 (rounded to three decimals).
Consider the table Student with attributes (rollNum, name, gender, marks). The primary key is rollNum. The SQL query is: 
SELECT *
FROM Student
WHERE gender = 'F' AND marks > 65;
The number of rows returned by this query is:

A database has 25,000 fixed-length records of 100 bytes (primary key 15 bytes). The data file is block-aligned so each record is fully contained within a block. The file is indexed by a primary index file, also block-aligned and ordered. Block size is 1024 bytes and a block pointer is 5 bytes. Each index entry stores the block’s anchor key (15 bytes) and a pointer (5 bytes). Binary search on an index file of \(b\) blocks needs \(\lceil \log_2 b \rceil\) block accesses in the worst case. Given a key, the number of block accesses required to identify the data file block that may contain the record, in the worst case, is ____________.