Start learning 50% faster. Sign in now
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.
Which blood group is the universal recipient?
A positively charged particle enters a uniform electric field directed downward. The force acting on the particle is:
What is the focal length of a plane mirror?
In Bernoulli's principle, increase in fluid velocity leads to:
A fish is at a depth d below the surface of a water tank. A cat observes the fish from air. Due to refraction at water-air interface, the apparent depth...
Biogas which is used for cooking purpose is a mixture of which of the following two components?
Which of the following statements about holes is incorrect ?
Which of the following reproduces using fission?
Which of the following correctly represents the order of increasing wavelength?
A heating element using nichrome connected to a 230 V supply draws an initial current of 3.2 A which settles after a few seconds to a steady value of 2....