WITH keys as (select 
o.conname,
(select nspname from pg_namespace where oid=m.relnamespace) as key_schema,
m.relname as key_table, 
m.oid as key_table_oid,
o.conkey AS key_col
from pg_constraint o inner join pg_class c on c.oid = o.conrelid
inner join pg_class m on m.oid = o.conrelid
where o.contype in ('u','p','f')  and o.conrelid in (select oid from pg_class c where c.relkind = 'r')),
keys_unnest as (select conname, key_schema, key_table, key_table_oid, key_col, key_col_num, ordin
from keys, unnest(keys.key_col) with ordinality as k(key_col_num, ordin)),
keys_with_names as (select key_schema as table_schema, key_table as table_name, a_key.attname as column_name
from keys_unnest k inner join pg_attribute a_key on k.key_col_num = a_key.attnum and k.key_table_oid = a_key.attrelid and a_key.attisdropped = false),

nn AS (SELECT c.table_schema, c.table_name, c.column_name,  c.data_type, c.is_nullable
FROM information_schema.columns AS c
WHERE (c.table_schema, c.table_name) IN (SELECT table_schema, table_name
FROM INFORMATION_SCHEMA.tables WHERE table_type='BASE TABLE') 
AND c.table_schema NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL)
AND NOT EXISTS (SELECT 1
FROM keys_with_names  AS kwn
WHERE kwn.table_schema=c.table_schema AND kwn.table_name=c.table_name AND kwn.column_name=c.column_name))

SELECT column_name, data_type, Count(*) AS total_columns, string_agg(table_schema || '.' || table_name || ' ' || CASE WHEN is_nullable='YES' THEN 'Nullable' ELSE 'Not nullable' END,';<br>' ORDER BY is_nullable, table_schema, table_name) AS columns_and_nullability
FROM nn
WHERE EXISTS (SELECT 1 FROM nn AS n WHERE n.column_name=nn.column_name AND n.data_type=nn.data_type AND is_nullable='YES')
AND EXISTS (SELECT 1 FROM nn AS n WHERE n.column_name=nn.column_name AND n.data_type=nn.data_type AND is_nullable='NO')
GROUP BY column_name, data_type
HAVING Count(DISTINCT is_nullable)>1
ORDER BY Count(*) DESC, column_name, data_type;