What is the total amount of mail traffic and the average size of each message?
mysql>
mysql> CREATE TABLE mail
-> (
-> t DATETIME, # when message was sent
-> senderUser CHAR(8), # sender (source user and host)
-> senderHost CHAR(20),
-> recipientUser CHAR(8), # recipient (destination user and host)
-> recipientHost CHAR(20),
-> size BIGINT, # message size in bytes
-> INDEX (t)
-> );
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> INSERT INTO mail (t,senderHost,senderUser,recipientHost,recipientUser,size)
-> VALUES
-> ('2010-05-11 10:15:08','saturn','barb','mars','tricia',58274),
-> ('2010-05-12 12:48:13','mars','tricia','venus','gene',194925),
-> ('2010-05-12 15:02:49','mars','phil','saturn','phil',1048),
-> ('2010-05-13 13:59:18','saturn','barb','venus','tricia',271),
-> ('2010-05-14 09:31:37','venus','gene','mars','barb',2291),
-> ('2010-05-14 11:52:17','mars','phil','saturn','tricia',5781),
-> ('2010-05-14 14:42:21','venus','barb','venus','barb',98151),
-> ('2010-05-14 17:03:01','saturn','tricia','venus','phil',2394482),
-> ('2010-05-15 07:17:48','mars','gene','saturn','gene',3824),
-> ('2010-05-15 08:50:57','venus','phil','venus','phil',978),
-> ('2010-05-15 10:25:52','mars','gene','saturn','tricia',998532),
-> ('2010-05-15 17:35:31','saturn','gene','mars','gene',3856),
-> ('2010-05-16 09:00:28','venus','gene','mars','barb',613),
-> ('2010-05-16 23:04:19','venus','phil','venus','barb',10294),
-> ('2010-05-17 12:49:23','mars','phil','saturn','tricia',873),
-> ('2010-05-19 22:21:51','saturn','gene','venus','gene',23992)
-> ;
Query OK, 16 rows affected (0.00 sec)
Records: 16 Duplicates: 0 Warnings: 0
mysql>
mysql>
mysql> SELECT SUM(size) AS 'total traffic',
-> AVG(size) AS 'average message size'
-> FROM mail;
+---------------+----------------------+
| total traffic | average message size |
+---------------+----------------------+
| 3798185 | 237386.5625 |
+---------------+----------------------+
1 row in set (0.00 sec)
mysql>
mysql>
mysql> drop table mail;
Query OK, 0 rows affected (0.00 sec)
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