Introduction To Database Questions and Answers

Answer: A

Correct answer: True

A database stores the definitions of its own structure - tables, columns, data types, keys, indexes - as metadata in system tables, right alongside the user data. That is what “self-describing” means, and it is why a tool can inspect an unfamiliar database without any external documentation.

Answer: D

Correct answer: Database Application and Database

The DBMS is the layer between the application and the database. The application issues requests; the DBMS carries them out against the stored data, applying security, integrity and concurrency rules on the way.

Answer: B

Correct answer: Print files on paper

A report generator takes data from the database and formats it for output - headings, grouping, subtotals, page breaks. It is a presentation tool: it does not update, insert or delete anything.

Answer: C

Correct answer: (A) and (B) both are true

A relation is a set of tuples, and two things follow from that. The order of the rows carries no meaning, so a query must sort explicitly if it wants a particular order; and no two rows can be identical, since a set has no duplicates. (SQL tables relax the second rule unless a key or DISTINCT enforces it.)

Answer: B

Correct answer: False

There is one more layer. Users interact with applications, applications call the DBMS, and only the DBMS touches the data. Applications never read or write the database files themselves - if they did, there would be no way to enforce security, integrity or concurrency.

Answer: B

Correct answer: Data

A database is fundamentally an organised collection of related data, held so that it can be stored, retrieved and managed efficiently. The programs that operate on it are the DBMS and the applications, which are distinct from the database itself.

Answer: B

Correct answer: Data record.

A record is a group of related fields describing one thing - a customer’s name, address and account number together. Records of the same kind are then grouped into a file, or in relational terms fields are columns, records are rows and the file is a table.

Answer: C

Correct answer: Combination of selection and Cartesian product

A natural join is built from the basic operators: form the Cartesian product of the two relations, then select the tuples whose common attributes are equal - and finally project away the duplicated columns. That is why the join is a derived operation rather than a primitive of relational algebra.

Answer: D

Correct answer: Sub schema.

A subschema (external schema) is one application’s view of the database: the subset of tables and columns it needs, possibly renamed or restructured. Several subschemas can sit over one logical schema, which is how different applications share the same data while each seeing only its own part.

Answer: C

Correct answer: Relational algebra

Relational algebra is the procedural set of basic operations - selection, projection, union, set difference, Cartesian product, and the joins and intersection derived from them. Relational calculus is the non-procedural counterpart: it describes what is wanted rather than how to compute it, and the two have equivalent expressive power.