I have MS SQL 2008 R2, 500 databases. What is the most efficient, easiest and \'modern\' way to query all databases sizes.
The output should have columns:
IF OBJECT_ID('tempdb.dbo.#space') IS NOT NULL
    DROP TABLE #space
CREATE TABLE #space (
      database_id INT PRIMARY KEY
    , data_used_size DECIMAL(18,2)
    , log_used_size DECIMAL(18,2)
)
DECLARE @SQL NVARCHAR(MAX)
SELECT @SQL = STUFF((
    SELECT '
    USE [' + d.name + ']
    INSERT INTO #space (database_id, data_used_size, log_used_size)
    SELECT
          DB_ID()
        , SUM(CASE WHEN [type] = 0 THEN space_used END)
        , SUM(CASE WHEN [type] = 1 THEN space_used END)
    FROM (
        SELECT s.[type], space_used = SUM(FILEPROPERTY(s.name, ''SpaceUsed'') * 8. / 1024)
        FROM sys.database_files s
        GROUP BY s.[type]
    ) t;'
    FROM sys.databases d
    WHERE d.[state] = 0
    FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 1, 2, '')
EXEC sys.sp_executesql @SQL
SELECT
      d.database_id
    , d.name
    , d.state_desc
    , d.recovery_model_desc
    , t.total_size
    , t.data_size
    , s.data_used_size
    , t.log_size
    , s.log_used_size
FROM (
    SELECT
          database_id
        , log_size = CAST(SUM(CASE WHEN [type] = 1 THEN size END) * 8. / 1024 AS DECIMAL(18,2))
        , data_size = CAST(SUM(CASE WHEN [type] = 0 THEN size END) * 8. / 1024 AS DECIMAL(18,2))
        , total_size = CAST(SUM(size) * 8. / 1024 AS DECIMAL(18,2))
    FROM sys.master_files
    GROUP BY database_id
) t
JOIN sys.databases d ON d.database_id = t.database_id
LEFT JOIN #space s ON d.database_id = s.database_id
ORDER BY t.total_size DESC
Not to steal your answer and adapt it for points or anything, but here is another factorization:
select d.name, 
    sum(m0.size*8.0/1024) data_file_size_mb, 
    sum(m1.size*8.0/1024) log_file_size_mb 
from sys.databases d
inner join sys.master_files m0 on m0.database_id = d.database_id
inner join sys.master_files m1 on m1.database_id = d.database_id
where m0.type = 0 and m1.type = 1
group by d.name, d.database_id
order by d.database_id
The following code worked for me very well.
    SELECT
        D.name As DbName,
        F.Name AS FullDbName,
        CASE WHEN F.type_desc='ROWS' THEN 'mdf' ELSE 'ldf' END AS FileType,
        F.physical_name AS PhysicalFile,
        CONVERT(DATE,D.create_date) AS CreationDate,
        F.state_desc AS OnlineStatus,
        CAST((F.size*8)/1024 AS VARCHAR(26)) + ' MB' AS FileSize_MB,
        CAST(F.size*8 AS VARCHAR(32)) + ' Bytes' AS FileSize_Bytes,
        CAST(CAST(ROUND((F.size*8)/(1024.0*1024.0),0) AS INT) AS VARCHAR(32)) + ' GB' AS FileSize_GB
    FROM 
        sys.master_files F
        INNER JOIN sys.databases D ON D.database_id = F.database_id
    ORDER BY
         D.name