How can I use a default value in a Select query in PostgreSQL?

I would like to use a default value for a column that should be used if no rows is returned. Is that possible in PostgreSQL? How can I do it? Or is there any other way I can solve this?

E.g. something like this:

SELECT MAX(post_id) AS max_id DEFAULT 0 FROM my_table WHERE org_id = 3

And if there is no rows with org_id = 3 in the table I want to return 0.

SELECT coalesce(MAX(post_id),0) AS max_id FROM my_table WHERE org_id = 3

or

SELECT case count(*) when 0 then 0 else MAX(post_id) end AS max_id
FROM my_table 
WHERE org_id = 3;

if you want max(post_id) to be null when there is 1 row but post_id is null

dbfiddle

StackExchange Database Administrators Q#2804, answer score: 68