is there a way to get ROOT on sql injection??

[17]

i can access to the database but not tables, im using sqlmap btw


+----------------+---------+
| Table | Entries |
+----------------+---------+
| `member` | 30389 |
| po_info | 18287 |
| wishlist | 17585 |
| product_size | 17079 |
| po | 15647 |
| product | 5680 |
| voucher | 78 |
| sub_category | 17 |
| employee | 16 |
| article | 11 |
| category | 6 |
| branch | 5 |
| goldrate_price | 5 |
| payout | 5 |
| banner | 3 |
| location | 3 |
| payout_info | 2 |
| page | 1 |
| setup | 1 |
+----------------+---------+

but when im trying to access it , it show this warning

[WARNING] the SQL query provided does not return any output
[16:22:23] [WARNING] in case of continuous data retrieval problems you are advised to try a switch '--no-cast' or switch '--hex'
[16:22:23] [WARNING] unable to retrieve column names for table 'po_info' in database 'secret_database'


all of this method not working:

-no-cast not working
-hex not working
-tamper not working
-flush-session same


help me