What is the difference between CHAR and VARCHAR2 in SQL?
This question tests understanding of data types and storage optimization. It evaluates whether a candidate knows when to use fixed-length versus variable-length strings.
Why Interviewers Ask This
Interviewers ask this to assess fundamental knowledge of database design and efficiency. They want to ensure you understand how different data types impact storage space and performance. Knowing the distinction helps in optimizing table schemas for large datasets where space matters.
How to Answer This Question
Start by defining both types clearly. Explain that CHAR is fixed-length and pads with spaces, while VARCHAR2 is variable-length. Discuss storage implications and give a concrete example of when to use each, such as using CHAR for country codes and VARCHAR2 for names.
Key Points to Cover
- CHAR is fixed-length with padding
- VARCHAR2 is variable-length without padding
- Storage efficiency differences
- Use cases for each type
Sample Answer
CHAR stores fixed-length data and automatically pads extra spaces to reach the defined length, which can waste storage if values vary significantly. VARCHAR2 stores variable-length data without padding, saving space by o…
Common Mistakes to Avoid
- Confusing them with TEXT types
- Ignoring storage overhead of CHAR
- Not mentioning padding behavior
Sound confident on this question in 5 minutes
Answer once and get a 30-second AI critique of your structure, content, and delivery. First attempt is free — no signup needed.