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DADay 40: 10 Characters ≠ 10 Bytes 😮💨 LENGTH vs CHAR_LENGTH
Everyone thinks name limits are SIMPLE…
Until Unicode enters the database 👀
Characters ❌
Bytes ❌
Emoji ❌
Regional letters ❌
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Interview Question
A system allows employee names up to 10 characters,
but the database column is limited to 10 bytes.
Why does this cause errors?
Which function would you use to detect risky names?
Sounds basic?
This is where candidates slip 👇
❌ Common Mistakes
❌ Assuming characters = bytes
❌ Using CHAR_LENGTH for storage validation
❌ Ignoring Unicode data
❌ Learning SQL only at surface level
SELECT LENGTH(employee_name)
FROM employees;
✔ LENGTH checks bytes
✔ Detects Unicode overflow
✔ Prevents insert failures
✔ Production-safe logic
SELECT CHAR_LENGTH(employee_name)
FROM employees;
👉 Counts characters (display logic, not storage)
🎯 Why Interviewers Ask This
Tests:
✔ Unicode awareness
✔ Storage vs display difference
✔ Real-world SQL thinking
✔ System design basics
Simple on paper.
Dangerous in production 🧠
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