Hi,

Yes, You can access the Odoo 16 PostgreSQL database using SQL if you're hosting on Odoo.sh or on-premise. Odoo Online (SaaS) does not provide SQL access for security and data integrity reasons.

Access requires valid PostgreSQL credentials and network permission to connect to the server. You can use tools like pgAdmin, DBeaver, or the psql command-line utility to explore the database. On Odoo.sh, database access is available through an SSH tunnel provided by the platform. 

Direct SQL changes bypass Odoo's ORM layer, meaning computed fields, workflows, and constraints won't trigger. This can result in data corruption, broken relationships, or inconsistent system behavior. Read-only SQL queries for reporting or BI tools are generally safe if no data is written or updated. Directly altering table structures or records may cause issues during upgrades or module installations. It's strongly recommended to use Odoo’s standard models or Studio tools for all business logic and data updates.

Hope it helps.