# 1、查看所有数据库大小

mysql> select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data_size from information_schema.TABLES;
+-----------+
| data_size |
+-----------+
| 2085.96MB |
+-----------+
1 row in set (0.00 sec)

# 2、查看指定数据库大小

mysql>  select table_schema,concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data_size from information_schema.TABLES where table_schema in ('db_test','dbtest_59') group by table_schema order by data_size desc;
+--------------+-----------+
| table_schema | data_size |
+--------------+-----------+
| dbtest_59    | 2060.28MB |
| db_test      | 0.27MB    |
+--------------+-----------+
2 rows in set (0.00 sec)

# 3、查看指定单表大小

mysql> select table_schema,table_name,concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data_size from information_schema.TABLES where table_schema='dbtest_59' group by table_name desc order by data_size desc;
+--------------+---------------------------------+-----------+
| table_schema | table_name                      | data_size |
+--------------+---------------------------------+-----------+
| dbtest_59    | testbl_auto_schedul_studet_info | 2057.00MB |
| dbtest_59    | testb_admin                     | 2.52MB    |
| dbtest_59    | testb_rbac_role_user            | 0.38MB    |
| dbtest_59    | testb_rbac_role_access          | 0.36MB    |
| dbtest_59    | testb_rbac_role                 | 0.02MB    |
| dbtest_59    | dy_students_info                | 0.02MB    |
+--------------+---------------------------------+-----------+
6 rows in set (0.00 sec)

# 4、查询数据库大小

select table_schema,concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data_size,table_name,table_rows from information_schema.TABLES  where table_schema   IN('dbtest_59') group by table_name order by table_rows desc;
mysql> select table_schema,concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data_size,table_name,table_rows from information_schema.TABLES  where table_schema   IN('dbtest_59') group by table_name order by table_rows desc;
+--------------+-----------+---------------------------------+------------+
| table_schema | data_size | table_name                      | table_rows |
+--------------+-----------+---------------------------------+------------+
| dbtest_59    | 2057.00MB | fudao_auto_schedule_course_info |    1497236 |
| dbtest_59    | 2.52MB    | fudao_admin                     |      10406 |
| dbtest_59    | 0.38MB    | fudao_rbac_role_user            |       7778 |
| dbtest_59    | 0.36MB    | fudao_rbac_role_access          |       3534 |
| dbtest_59    | 0.02MB    | fudao_rbac_role                 |         70 |
| dbtest_59    | 0.02MB    | dy_homework_info                |          0 |
+--------------+-----------+---------------------------------+------------+
6 rows in set (0.00 sec)