Danny’s Diner SQL Case Study

Business Context: A restaurant needs customer insights to drive loyalty program decisions.

SQL Skills Demonstrated:

• Complex JOINs (LEFT, INNER) across multiple tables
• Window functions (DENSE_RANK, RANK) for ranking and partitioning
• Date-based filtering and aggregations
• CASE statements for conditional logic
• CTEs (Common Table Expressions) for query optimization
• Advanced point calculation logic with business rules

Key Accomplishments:

• Solved 10 core questions covering customer spending, visit frequency, and preferences
• Implemented sophisticated loyalty point system with time-based multipliers
• Created member status indicators with membership timeline analysis
• Generated denormalized views for business intelligence