SQL

Relational stuff: normalization, joins, complex queries…

SQL Queries

… basic stuff…

Useful More Advanced Stuff for Analytical Engineers

• GROUP BY, HAVING

  • Conditional aggregation (SUM(CASE WHEN …))

• Window Functions (very common)

  • ROW_NUMBER, RANK, DENSE_RANK
  • LAG / LEAD
  • Running totals (SUM() OVER (...))
  • Partitioning vs ordering

Typical Question Patterns

• “Top N per group”
• “Find duplicates / latest record per key”
• “Compute metrics over time”
• “Sessionization / rolling metrics”