Reporting Database Sizes

I frequently need to pull size information about a large number of databases. OEM has an interesting capacity planning feature, but some times I just want the raw data. This is the base query I start with and add on additional information or slice it in different ways to fit what I need. I run this in the OEM repository.

col target_name for 130
SELECT target_name, SUM (maximum)
    FROM sysman.mgmt$metric_daily t
   WHERE     target_type IN ('oracle_database', 'rac_database')
         AND metric_column IN ('spaceAllocated')
         AND TRUNC (rollup_timestamp) = TRUNC (SYSDATE) - 1
         AND UPPER (target_name) LIKE '%&1%'
GROUP BY target_name
ORDER BY target_name

This gives you the size, by database as of the previous day.