No, that isn't correct. The query planner optimises query execution in a layer of abstraction below the representation of the tables, the relational integrity and structure of the user-accessible objects.

Tables, their attributes, relationships etc. are easily able to be represented visually. Entity-Relationship Diagrams have standard notation (Chen, Crows-foot, UML). We can represent models conceptually, logically or physically, we can even indicate the existence of views and indexes. In terms of queries, DML is essentially multi-filtered, multi-dimensional slicing of tables and can be represented as output sets which are as modellable as the source tables.

On the wider point, DBT looks promising. It seems to be a good middle ground between the purists (like me) who wish back-end devs would just learn how to model data, and the adventurists who prefer to lock everything behind OOP principles.