Postgres DB Size Command

Question

What is the command to find the size of all the databases?

I am able to find the size of a specific database by using following command:

Answer 1

From the PostgreSQL wiki.

---

_{NOTE: Databases to which the user cannot connect are sorted as if they were infinite size.}

SELECT d.datname AS Name,  pg_catalog.pg_get_userbyid(d.datdba) AS Owner,
    CASE WHEN pg_catalog.has_database_privilege(d.datname, 'CONNECT')
        THEN pg_catalog.pg_size_pretty(pg_catalog.pg_database_size(d.datname))
        ELSE 'No Access'
    END AS Size
FROM pg_catalog.pg_database d
    ORDER BY
    CASE WHEN pg_catalog.has_database_privilege(d.datname, 'CONNECT')
        THEN pg_catalog.pg_database_size(d.datname)
        ELSE NULL
    END DESC -- nulls first
    LIMIT 20

---

The page also has snippets for finding the size of your biggest relations and largest tables.