SQLGROUP BYaggregationtutorial
What is GROUP BY in SQL? Grouping rows for beginners
GROUP BY is the SQL command for "collapse rows into groups and aggregate". Plain words: how to get "how many orders each customer has" in a single query. What you can and can't put in SELECT, the difference from DISTINCT, GROUP BY on multiple columns, and common pitfalls.
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GROUP BYis the SQL command for "collapse identical rows into one and aggregate them". The basic way to get stats: how many orders each customer has, total sales per product, average salary per department.This article is currently in Russian. The full English translation is on the way.