- To group records based on a specified field
- To unify events from different tables
- To summarize key fields in event tables
The correct answer is: To unify events from different tables
Explanation: A primary usage of the UNION ALL function in AMC queries is to unify events from different tables. This allows you to combine rows from multiple event sources (such as impressions, clicks, and conversions) into a single result set for analysis, preserving all records from each table without removing duplicates.
Reference content: From Amazon’s official documentation: AMC SQL Reference – UNION ALL
“Use UNION ALL to combine results from different tables, such as when you need to analyze event-level records (impressions, clicks, conversions) together. … The UNION ALL statement retains all rows from each query, allowing for unified or cross-event analysis.”