SELECT table_schema "database", sum( data_length + index_length )/1024 /1024 "Data Base Size in MB", sum( data_free )/1024 /1024 "Free Space in MB"
FROM information_schema.TABLES
GROUPBY table_schema


   这里就返回当前各数据库的占用空间大小，包括data_length+inddex_length,
data_length为存放表的索引