Why might a database designer choose a composite primary key instead of a single-column primary key?

hard📝 Conceptual Q10 of 15

SQL - Table Constraints

ABecause composite keys automatically create indexes on all columns

BBecause no single column uniquely identifies a record alone

CBecause composite keys allow NULL values in primary key columns

DBecause composite keys improve query speed in all cases

Step-by-Step Solution

Solution:

Step 1: Understand uniqueness requirement
A primary key must uniquely identify each record.
Step 2: Reason for composite keys
If no single column is unique alone, combining columns as a composite key ensures uniqueness.
Final Answer:
Because no single column uniquely identifies a record alone -> Option B
Quick Check:
Composite keys = uniqueness from multiple columns [OK]

Quick Trick: Use composite keys when single column isn't unique [OK]

Common Mistakes:

MISTAKES

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