Handle Missing Customer Profile Data with COALESCE in SQL

Question

Write a SQL query on `customers` that returns `customer_id`, `customer_name`, and a computed column `contact_channel`. If `email` is present, display `email`. If `email` is NULL, fallback to `phone_number`. If both are NULL, display 'Missing Contact'.

Accepted Answer

Optimal Solution:
SELECT 
  customer_id, 
  customer_name,
  COALESCE(email, phone_number, 'Missing Contact') AS contact_channel
FROM customers
ORDER BY customer_id ASC;

Technical Explanation:
The `COALESCE` function evaluates arguments in sequential order and returns the first non-null expression. If both email and phone_number are null, the literal string 'Missing Contact' is returned.

customer_id	customer_name	contact_channel
1	Aditi Sharma	aditi@gmail.com
2	Rahul Verma	+919711111111
3	Sneha Patel	Missing Contact

customer_id	customer_name	email	phone_number
1	Aditi Sharma	aditi@gmail.com	+919800000000
2	Rahul Verma	NULL	+919711111111
3	Sneha Patel	NULL	NULL