You now have the SQL skills for DE interviews.
Window functions: ROW_NUMBER, RANK, LAG/LEAD, running aggregates.
CTEs: Break complex queries into readable steps.
Optimization: Filter early, use indexes, avoid functions on indexed columns.
Patterns: Running totals, gap/island, sessionization.
At scale: Partitioning and clustering matter more than clever queries.
Next: Learn data modeling fundamentals.