select random COLUMN from PostgeSQL

I have a table which contains some links to photos in a few columns and I need to get a random photo from it.

SELECT photo_front, photo_left, photo_rear FROM photos ORDER BY RANDOM () LIMIT 1

gives me a 3 links. But can I get only 1 random out of it?

Answer

You can unpivot. For instance:

SELECT v.photo
FROM photos p CROSS JOIN LATERAL
     (VALUES (photo_front), (photo_left), (photo_rear)
     ) v(photo)
ORDER BY RANDOM()
LIMIT 1;

If the columns can ever be NULL, then you might want WHERE v.photo IS NOT NULL.

I should note that using ORDER BY RANDOM() is an expensive operation. You are using that in your query and so performance does not seem to be an issue.