Context

Analysts often summarize operational error data in Excel using pivot tables and formulas. In SQL interviews, the equivalent skill is turning raw rows into grouped summaries and, when needed, pivot-style report columns.

Core Question

Explain how you would summarize partner error data in SQL in a way that mirrors Excel pivot tables and formulas. Your answer should cover:

1. How to group raw error records by partner and error type
2. How to calculate counts, totals, and percentages
3. How to create pivot-style output in PostgreSQL using conditional aggregation
4. When SQL is preferable to Excel for this task

Scope Guidance

The interviewer is not looking for advanced dynamic SQL. Focus on clear explanations of GROUP BY, aggregate functions, CASE WHEN, and how these replace common Excel pivot table workflows for reporting and analysis.