SQL as a business analysis tool

The idea

Start with a precise business question, population, time window and metric definition. Identify the source tables and join keys; check duplicates, missing values and event timing before interpreting a count. A query result is evidence only when the denominator and data quality assumptions are clear.

Example

To measure onboarding completion, count distinct applicants who started in a cohort and reached activation within seven days. Exclude test accounts and separate retries from unique people.

Illustrative BA scenario

Fictional mobile banking example: an apparent registration drop is caused by a changed event name, not customer behaviour. Validating the tracking specification prevents a false product decision.

Try it yourself

1. Define numerator and denominator for a completion KPI.
2. Write a SQL question that compares failures by device, not just total failures.