SQL BI & Reporting

When to Use

• Writing summary reports with subtotals across multiple dimensions
• Building time-series queries (bucketing, gap filling, moving averages)
• Pivoting row data into columns or unpivoting columns into rows
• Generating date ranges or number sequences (tally tables)
• Solving gaps-and-islands problems (consecutive ranges, session analysis)
• Exporting query results as JSON, XML, or CSV
• Writing queries optimized for Power BI DirectQuery or SSRS
• Year-over-year, cohort, or funnel analysis

When NOT to use: application schema design (table design, naming conventions, access control), query performance tuning (execution plans, index tuning, wait stats), or ETL pipeline design.

Multi-Level Aggregation

Three operators produce subtotals from a single GROUP BY — choose based on your needs: