SQL Patterns (High Frequency)

This page is about patterns, not syntax.

Pattern 1: Deduplicate latest row

Approach:

• define partition key
• order by timestamp
• pick row_number = 1

Pattern 2: Funnel conversion

Approach:

• define steps
• join events per user/session
• compute drop-off

Pattern 3: Cohort retention

Approach:

• cohort by first event date
• compute retention by week/month

Mistakes to avoid

• accidental row multiplication
• filtering too early (before dedupe)
• wrong grain