Using n_distinct to Extract Unique Values by Specific Conditions in R Data Analysis

Optimizing the SQL Query Riddle: A Deep Dive into Data Modeling and T-SQL

Understanding Grouping and Aggregation in SQL: A Deep Dive into Using `GROUP BY` with Additional Columns

Transforming Data from Long Format to Wide Format Using dcast() in data.table

Solving the "All In" Group By Problem with SQL Aggregation and COALESCE