Capstone Challenge 1: Clean Contact List

You're building a production-ready contact list from messy CRM data. Every field needs cleaning.

🛠️ Techniques You'll Combine

Column	Technique	Example
full_name	TRIM + concatenation	<code>TRIM(first_name)	' '	TRIM(last_name)</code>
clean_email	LOWER + TRIM + COALESCE	<code>COALESCE(LOWER(TRIM(email)), 'N/A')</code>
clean_phone	Nested REPLACE + COALESCE	Remove -, (, ), spaces
source	LOWER + TRIM	Standardize categories

💡 COALESCE Reminder

COALESCE(value, 'N/A') returns 'N/A' when value is NULL — perfect for display-ready output.

⚠️ Phone Cleaning

You need to chain multiple REPLACE calls:

REPLACE(REPLACE(REPLACE(phone, '-', ''), '(', ''), ')', '')

Requirements:

• full_name: Trimmed first + last name, properly formatted
• clean_email: Lowercase, trimmed email (or 'N/A' if null)
• clean_phone: Phone with formatting removed (or 'N/A' if null)
• source: Standardized source (lowercase, trimmed)

Order by full_name, limit to 15.