How to join v$database with v$instance

Here is a useful query which displays basic information about the database, using v$database and v$instance.
Take the opportunity to calculate the uptime for the database by subtracting the value of startup_time from the current date.

col platform_name format a30
col open_mode format a20
col host_name format a20
col version format a10
col status format a20
col uptime format a30
col name format a10
set lines 300

SELECT D.NAME,D.PLATFORM_NAME,D.CREATED, D.OPEN_MODE,I.HOST_NAME,I.VERSION, I.ARCHIVER,I.STATUS,
   TO_DSINTERVAL( TO_CHAR(
                                    TO_TIMESTAMP(SYSDATE)-I.STARTUP_TIME
                                   )
                      ) "UPTIME", 
                      (SELECT ROUND(SUM(BYTES)/1024/1024/1024) FROM DBA_DATA_FILES) "DB size GB",  
                      ( SELECT ROUND(BYTES/1024/1024/1024) "mem GB" FROM V$SGAINFO WHERE NAME = 'Maximum SGA Size' ) "SGA max size GB"
  FROM V$DATABASE D INNER JOIN V$INSTANCE I 
  ON UPPER(D.NAME) = UPPER(I.INSTANCE_NAME);

Result may look like the following:

NAME	PLATFORM_NAME	CREATED	OPEN_MODE	HOST_NAME	VERSION	ARCHIVER	STATUS	UPTIME	DB size GB	SGA max size GB
proddb01	Linux x86 64-bit	10.12.2015 14:16:46	READ WRITE	prodserver01.mycompany.com	11.2.0.4.0	STARTED	OPEN	+00 13:59:55.000000	929	12