Grouping By Nothing In SQL

Lukas Eder points out a subtlety of the GROUP BY clause:

SELECT count(*)
FROM film
GROUP BY ()

This will yield:

count |
------|
1000  |

What’s the point, you’re asking? Can’t we just omit the GROUP BY clause? Of course, this will yield the same result:

SELECT count(*)
FROM film

Yet, the two versions of the query are subtly different.

Great post and also shows a case when GROUP BY () isn’t supported.