Why is this query unsuitable for assembling a rule-based audience of those who have completed a conversion event?SELECTuser_id FROM conversions

This query is unsuitable because it selects from a conversions table, which typically contains event-level data, not audience data. To build a rule-based audience in AMC, you need to select from an audience-specific table (e.g., audiencesegmentmemberships) or a table designed for audience activation that includes user identifiers and audience membership flags. The userid can be included as a dimension in the SELECT statement, as it's crucial for identifying audience members. A GROUP BY statement is not inherently required for simply selecting user IDs for an audience, though it might be used in more complex audience definitions involving aggregations. The core issue is selecting from the wrong type of table for audience assembly.