PostgreSQL we can retrieve all tables,columns as
``` sql
SELECT n.nspname as Schema,
  c.relname as Name,
  a.attname as Col 
FROM pg_catalog.pg_class c
     LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
     LEFT JOIN pg_catalog.pg_attribute a ON a.attrelid = c.relname::regclass    
WHERE
       n.nspname <> 'pg_catalog'
      AND n.nspname <> 'information_schema'
      AND n.nspname !~ '^pg_toast'
  AND pg_catalog.pg_table_is_visible(c.oid)
  AND c.relkind = 'r'
  AND a.attnum > 0
ORDER BY 1,2
;
```