Test: Database Concepts - 2 - SSC CGL MCQ

In a relational database, a key is a column or set of columns used to uniquely identify rows in a table. This is crucial for maintaining data integrity and establishing relationships with other tables. By uniquely identifying rows, keys ensure that each record in a table can be accessed and managed accurately.

The degree of a relation in a relational database represents the number of attributes (columns) in each tuple or row of the table. It indicates the complexity and structure of the data stored within the database. A higher degree implies more attributes associated with each data entry, providing detailed information about the entities being represented.

In relational databases, a domain refers to the set of all possible values that an attribute or column in a table can hold. It defines the range of valid data entries for a particular field, ensuring data consistency and integrity within the database. Domains help enforce data constraints and maintain data quality in relational databases.

Relationships are established between tables in a relational database to reduce data redundancy. By linking related data across multiple tables, redundancy is minimized, leading to more efficient storage and improved data consistency. This relational approach helps maintain data integrity and facilitates data retrieval and manipulation.

The cardinality of a relation in a relational database signifies the number of tuples or rows present in that specific relation. It provides insight into the volume of data entries within the table, indicating the size and scale of the information stored in that particular entity.

Attributes in a relational database are the column headings in a table, each representing a specific characteristic or property of the data being stored. They define the structure of the data within the table and hold distinct values that describe the entities or objects the table represents.

Keys play a critical role in relational databases by uniquely identifying rows in a table. By providing a means to distinguish and access individual records, keys help maintain data consistency, enforce data integrity constraints, and facilitate efficient data retrieval operations within the database.

A Weak Entity Set in the Entity-Relationship Model is characterized by lacking sufficient attributes to form a primary key. Unlike Strong Entity Sets that have a primary key or enough attributes for unique identification, Weak Entity Sets rely on a partial key in conjunction with a discriminator to uniquely identify entities within the set.

In a relational database, a tuple refers to a single row or record in a relation, consisting of a set of values corresponding to the attributes defined for that particular table. Tuples represent specific instances of data entries within the database tables, encapsulating all the attribute values associated with a particular entity or object.