This user's frustration is a familiar one, and it exposes a fundamental misunderstanding that legacy spreadsheet tools have trained into us. The problem isn't that duplicate data exists, it's that the tool you're using demands a level of data hygiene that it never taught you to maintain. When Excel warns about duplicates during a relation (what most modern tools call a join or lookup), it isn't being helpful. It's revealing a structural weakness in how traditional spreadsheets handle relationships between tables.
You did exactly what any reasonable person would do: you used conditional formatting to find the duplicates. And when none turned red, you hit a wall. That wall isn't your fault. Conditional formatting checks for exact cell matches within a single column. But the duplicate warning for a relation is about referential integrity, whether every value in one table has a unique match in the other. You can have two identical team names in your Team-Name table and see no red highlights because conditional formatting compares cells, not records. The tool is giving you a warning about a problem it cannot help you solve.
This is where the gap between intention and execution becomes costly. You want to sort teams by total score in a separate table. That's a natural, simple request. But the spreadsheet you're using forces you to become a data architect before you can finish the task. You have to clean your data manually, ensure every name is unique, then rebuild your relation. An AI-native spreadsheet would look at your two tables, understand that "Team-Name" likely contains duplicates because teams appear multiple times, and ask if you want to create a unique list automatically. It would resolve the ambiguity before you ever saw a warning.
The practical takeaway is this: the tool you're using is designed for flat, manual workflows. When you try to build relationships, the kind of thinking that modern data work demands, it punishes you with error messages and demands you fix problems it could have prevented. Your time is better spent exploring a solution that treats duplicate data as a signal, not a roadblock. Start by checking whether your Team-Name table actually has unique entries for each team. If it doesn't, create a distinct list first. Then build your relation. That workaround will get you sorted. But ask yourself why you should have to do it at all.