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stage 4
sql mastery checklist
goal: set-based thinking.
phase 1 — fundamentals
- select all columns
- select specific columns
- filter with where
- sort with order by
- limit rows
- count rows
- max / min / avg
- basic conditions (between, like)
phase 2 — grouping
- group by city
- sum revenue per user
- max order per user
- count per day
- having clause
- filter grouped data
phase 3 — joins
- inner join users and orders
- left join with null handling
- users without orders
- product revenue aggregation
- top users by spending
- most sold product
- products never ordered
goal: relational clarity.
phase 4 — intermediate logic
- subqueries (above average spending)
- second highest value
- window function ranking
- running totals
- first order per user
- duplicate detection
- percentage contribution
window functions = intellectual maturity in sql.
phase 5 — business analysis
- cohort analysis
- retention rate
- churn detection
- category revenue per month
- anomaly detection vs user average
this is analytics engineering thinking.