Which of the following is true about database rows?
Information about the same instance can be split across rows
They contain information about many instances of the table
They contain information about only one instance of the table
None of the above statements are true about database rows
The Correct Answer and Explanation is:
The correct answer is:
They contain information about only one instance of the table.
Explanation:
In relational databases, a row (also called a record or tuple) represents a single, complete instance of the entity that the table is designed to store information about.
What is a database row?
- A database table is a collection of data organized into columns and rows.
- Each column corresponds to a specific attribute or field of the data (e.g., name, age, employee ID).
- Each row contains data values for all the columns, representing one unique instance of that entity (e.g., one employee’s details).
Why do rows contain information about only one instance?
- The fundamental design of relational databases follows the principle of atomicity: each cell in the table contains a single value, and each row corresponds to one entity or instance.
- For example, if a table is named
Employees, each row represents one employee with all their details (name, department, hire date, etc.). - This design makes data retrieval, updating, and management straightforward because each row is self-contained for a single entity.
What about the other options?
- “Information about the same instance can be split across rows”: This is generally false for a well-designed relational table because splitting the same instance across multiple rows would violate the principle of normalization. Data for one entity should be contained in a single row to avoid redundancy and maintain consistency.
- “They contain information about many instances of the table”: This is false because multiple instances (entities) are represented across multiple rows, not within a single row. A row is dedicated to one instance.
- “None of the above”: This is incorrect because the statement about rows containing information about only one instance is true.
Summary:
- Each row in a database table uniquely represents one instance of the entity described by the table.
- This design keeps data organized, easy to query, and consistent.
- Breaking up information for a single instance across rows would create confusion, redundancy, and complexity.