SQL NULLS LAST

Forces NULL values to the bottom — already the default for ASC, but not for DESC.

What & Why

NULLS LAST forces NULLs to the end of the sort. This already happens automatically with ASC in Postgres — but DESC's default is actually the opposite (NULLS FIRST), so this keyword matters most when sorting descending and still wanting NULLs at the bottom.

See How It Works

BUSINESS QUESTION

Sort product feedback from highest NPS score to lowest and keep missing scores at the bottom.

id	user_id	feature_id	rating	nps_score	comment	created_at
1	101	1	5	9	Clear and useful	2024-01-25 12:15:00+00
2	102	2	4	NULL	Export worked well	2024-02-20 15:40:00+00
3	103	1	4	7	Helpful setup flow	2024-03-18 09:05:00+00
4	104	3	3	NULL	Needs clearer timing	2024-04-08 17:30:00+00

EXAMPLE QUERY

SELECT id, user_id, nps_score FROM product.feedback
ORDER BY nps_score DESC NULLS LAST;

RESULT — NULLs last

id	user_id	nps_score
1	101	9
3	103	7
2	102	NULL
4	104	NULL

DESC sorts known scores high to low; NULLS LAST keeps missing values at the bottom.

Beginner business practice