Data Base Management System MCQs SET-2

Join is considered a derived or non-fundamental operator in relational algebra because it can be performed using a combination of Cartesian Product and Selection. Set Difference, Cartesian Product, and Rename are all fundamental operations.

In Entity-Relationship diagrams, Specialization (and Generalization) is represented using a triangle component labeled 'IS A', which connects the high-level entity to the low-level entities.

MySQL is one of the most popular open-source relational database management systems. SQL Server, Oracle, and MS Access are proprietary/commercial products developed by Microsoft and Oracle.

The DISTINCT keyword is used in a SELECT statement to eliminate duplicate rows from the results, ensuring that only unique values are returned.

In the data hierarchy, the order from lowest to highest is: Bit, Byte, Field, Record, File, and finally, Database, which is the collection of related files/tables.

A Candidate Key is defined as a minimal super key—meaning it is a super key such that no proper subset of its attributes is also a super key.

The SQL UPDATE command is part of the Data Manipulation Language (DML) and is used to modify the existing data within a table.

DDL (Data Definition Language) is used to define the database structure, including tables, schemas, and integrity constraints like Primary Key or Foreign Key.

In Entity-Relationship modeling, Ellipses (or Ovals) are used to represent attributes, Rectangles represent entities, and Diamonds represent relationships.

The ANSI-SPARC database architecture consists of three levels: the External level (user views), the Conceptual level (logical structure), and the Internal level (physical storage).

In relational database theory, a 'Relation' is the mathematical term for what is commonly known in practice as a 'Table'.

The Cartesian product (X) is a binary operator because it requires two input relations to produce a resulting relation containing all possible combinations of tuples.

SQL stands for Structured Query Language, which is the standard language for dealing with Relational Databases.

User data, metadata (data about data), and indexes are internal components of a database. Reports are external outputs or tools used to present data, not a core storage component of the database itself.

A Domain is the set of all unique values permitted for an attribute in a database column.

A View is a virtual table based on the result-set of an SQL statement. It does not store data physically; instead, it provides a way to look at data stored in base tables.

A Cross product (also known as Cartesian product) is a binary operator because it operates on two relations.

A Diamond-shaped box is used in E-R diagrams to represent the relationship between two or more entities.

To delete a column, you use the 'ALTER TABLE' command combined with 'DROP COLUMN'. 'DELETE' is used only for removing rows/records.

A Self-join is a regular join, but the table is joined with itself. This is often used to query hierarchical data within the same table.