SQL · Aggregation and grouping

group by expression

Groups by a computed value. PostgreSQL needs the same expression in SELECT.

sqlRunnable example sql course

Syntax

group by date_trunc('month', created_at)

Example

Open in the lab

-- PostgreSQL
-- SELECT date_trunc('month', created_at) AS month, count(*) FROM lessons GROUP BY 1;

SQLite equivalents use strftime().

Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.