select columns and its data types

hi,
how can i show all the columns and its data types?
i create the following sql-statement but it only gets me a reference of the data types, how can i replace the reference?

SELECT
    pg_class.relname, pg_attribute.attname, pg_attribute.atttypid
FROM
    pg_catalog.pg_attribute, pg_catalog.pg_class
WHERE
    pg_attribute.attrelid = pg_class.relfilenode

thanks!

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