Data Analyst
mediumdata-analyst-sql-joins-pitfalls
What are common SQL join pitfalls that cause incorrect metrics?
Answer
Common pitfalls:
- Many-to-many joins inflating counts
- Joining at the wrong grain
- Using INNER vs LEFT incorrectly
- Duplicates in dimension tables
Fix by validating row counts at each step, using distinct keys, and aggregating at the correct grain before joining.
Related Topics
SQLData ModelingAnalytics