You can group them all in the same alter statement:
alter table tbl alter col1 drop not null,
alter col2 drop not null,
…
You can also retrieve the list of relevant columns from the catalog, if you feel like writing a do block to generate the needed sql. For instance, something like:
select a.attname
from pg_catalog.pg_attribute a
where attrelid = 'tbl'::regclass
and a.attnum > 0
and not a.attisdropped
and a.attnotnull;
(Note that this will include the primary key-related fields too, so you’ll want to filter those out.)
If you do this, don’t forget to use quote_ident()
in the event you ever need to deal with potentially weird characters in column names.