Select Count

SELECT COUNT(*), sum(data_length), sum(index_length), sum(data_free) FROM information_schema.tables;

+----------+------------------+-------------------+----------------+
| COUNT(*) | sum(data_length) | sum(index_length) | sum(data_free) |
+----------+------------------+-------------------+----------------+
|      802 |        677396480 |         264617984 |      541065216 |
+----------+------------------+-------------------+----------------+
1 row in set (0.01 sec)