The optimizer can choose a star join plan only if a query involves tables from a star or snowflakeschema that meets the following requirements.
只有查询中包含满足以下要求的星型或雪花模式的表时,优化器才可以选择星型连接计划。
3
When you define a dimension based on a snowflakeschema, which is where dimension attributes are derived from multiple related tables, an attribute relationship is automatically defined as follows.