SQL GROUP BY Guide - Essential SQL

An overview of the SQL GROUP BY clause

GROUP BY SQL Queries to Summarize and Rollup Sets of Records

SQL Aggregate Functions Code Samples

Boi | Data Analytics • Mapping on Instagram: "My query had grown over time, i had added more joins, filters, aggregates and calculations until it became the slowest part of my stack. I tried everything: indexes, denormalization, query hints… nothing. The main Problem: A Bloated Analytical Query On a table with: * 5 million users * 50 million orders * 80 million login events It took over 12 seconds on average. The Fix: Reusable Inline CTEs The problem wasn’t just data volume , it was redundant jo

GROUP BY SQL query to get number of records, average , maximum minimum & sum over a group of records

SQL Average Function to Calculate Average of a set of SQL Server Rows