Optimizing Queries with SELECT COUNT(DISTINCT CASE WHEN ... THEN ... ELSE NULL END) and GROUP BY for Improved Performance in SQL.

Retrieving Course Data Based on User Count: A Comprehensive Approach

Counting Unique Values Per Month in R: A Step-by-Step Guide

Solving SQL Queries Involving String Prefixes: A Comparative Analysis of Concatenation and Joins

SQL Query to Find Customers Who Bought Specific Brands and Products in at Least Two Different Purchases