MySQL CASE Statement: Conditional Logic in Queries

CASE brings if-else logic into SQL. Analysts use it constantly to bucket values into categories, build pivot-style reports, and compute conditional metrics — all inside a single query.

Key Points

• Syntax: CASE WHEN salary >= 100000 THEN 'High' WHEN salary >= 50000 THEN 'Mid' ELSE 'Low' END
• Works in SELECT, WHERE, ORDER BY and inside aggregates
• Conditional aggregation: SUM(CASE WHEN status='paid' THEN amount ELSE 0 END)
• Pivot rows into columns using one CASE per column
• Custom sort: ORDER BY CASE priority WHEN 'urgent' THEN 1 … END
• Conditions evaluate top-down — order your WHENs carefully