Counting Distinct Units with Condition Based on Different Column in SQL

Finding Unique Values and Replacing Them: A Step-by-Step Guide to Data Cleaning with R

How to Fix "Group By" Error in DB2 Query with Distinct Count

Removing Duplicates from a Microsoft Access Table While Keeping One Record

Concatenating Distinct Strings and Numbers While Avoiding Duplicate Sums

Extract Distinct Data from SQL Tables Using Advanced Techniques