The ID field of table tbl represents car categories, with each category further divided into Brand and Type. The task is to group by ID and determine the source of differences within each group: if a group has multiple brands, Difference is "Brand"; if a group has multiple types, Difference is "...
Source: [Dev.to](https://dev.to/esproc_spl/sqlazy-identify-whether-differences-within-groups-come-from-brand-or-type-problem-description-4hj8)