How to set all table columns to NOT NULL at once?

Question

Is this even possible, if so how? if not then I would be happy with a way that doesn't require typing each column name one by one. My use-case is that I create a table from a query and would like to make all columns NOT NULL because I later do ORM using Slick and it is a lot nicer to have all those column types not null (and therefore non Option[X]). This is static data so the column values will not be null and won't change either.

Unlike MySQL, Postgres doesn't figure out that the originating query columns are all NOT NULL already.

I'd like to avoid in my script adding the constraint one by one and be prone to breaking the solution whenever the query schema is changed ie

CREATE TABLE dentistry_procedure AS SELECT * FROM ...
ALTER TABLE dentistry_procedure ALTER column * SET NOT NULL;

How?

Answer 1

You could use metadata table and build dynamic query:

SELECT format('ALTER TABLE %I '||STRING_AGG(format('ALTER COLUMN %I SET NOT NULL', COLUMN_NAME),CHR(13)||',')
              , MIN(TABLE_NAME))
FROM INFORMATION_SCHEMA.COLUMNS
WHERE IS_NULLABLE = 'YES'
  AND TABLE_NAME = 't';

db<>Fiddle demo