Question
Which of the following keys ensures that no duplicate
values are allowed and also uniquely identifies a record in a relational database table?Solution
The primary key is a critical concept in database design. It uniquely identifies each record in a table and enforces entity integrity. 1. Uniqueness: A primary key ensures that each record in the table has a unique identifier, preventing duplicates. 2. Non-Null Constraint: The primary key field cannot contain null values, ensuring every record is identifiable. 3. Database Operations: Many database operations, such as joins and lookups, rely on the primary key for accurate and efficient processing. 4. Example: In a table of employees, the EmployeeID column can serve as a primary key to uniquely identify every employee. These properties make the primary key indispensable for maintaining data integrity. Why Other Options Are Incorrect: • A) Foreign Key: Establishes a relationship between two tables but does not ensure uniqueness within a table. • B) Composite Key: Comprises two or more columns to uniquely identify a record but is not a primary key unless explicitly defined. • D) Alternate Key: A candidate key not chosen as the primary key, used as an alternate unique identifier. • E) Candidate Key: Represents all fields that can qualify as primary keys but lacks the enforced selection of the primary key.
Maximum profit is obtained at the point, where:
Red and Far-red light absorbing, bluish photoreceptor, which is present in the cytosol of plants, is:
………………………. a flagship initiative of the Ministry of Agriculture and Farmers Welfare, has won the Platinum Award in the Digital Empower...
Which among the following is the largest source of irrigation in India, apart from rains?
One horse power is equal to-
Which project assesses the impact of climate change on agriculture in India?
What is the amount of food grains given to each poor family per month under the targeted public distribution system?
What is the estimated total milk production in India for the year 2023-24 according to the "Basic Animal Husbandry Statistics 2024"?
What percentage of the unit cost is covered by the Pradhan Mantri Matsya Sampada Yojana (PMMSY) for general beneficiaries?
Best time for sowing deep water rice is