H2 SELECT NULLABLE or other equivalent to check a column has NOT NULL constraint or not
If you have a definition like this:

create table foo 
(
   id integer not null
)


The following query will show "NO" in the is_nullable column:

select table_name, 
       column_name,
       is_nullable
from information_schema.columns


If the column has a check constraint, like this:

create table foo
(
  id integer,
  constraint id_not_null check (id is not null)
);


then this will be shown as "nullable" with the first query. You would need to check information_schema.constraints and analyze the content of the CHECK_EXPRESSION column to detect this.