> entities are fundamentally different from tables

Isn't the fact that they are _mostly_ interchangeable the foundational principle of hundreds of ORMs? Of course the DDL doesn't say much about the entity's lifecycle, but if the bar is set at representing its relationships, fields and cardinality as a graph, it seems sufficient?

To make parent’s point more exact: from Chen’s definition, these ER diagrams derived from SQL are the “physical” (most low-level) diagrams, you cannot recreate the “logic” or “conceptual” diagrams from it.

I guess nowadays few people care about this difference.

Can you please elaborate on the differences? They are practically interchangeable, but conceptually there might be another layer on top of entities and relationships for somewhat richer semantics (like describing a relation, or additional annotations on the entity)

the use case for sql to er, is to study a database new to you

so the db already exist, but they have no er, and maybe even little docs

so it act more like an exploratory tool, ideally, it should allow you to create views and add notes, so you dont have to look at the full er at once, especially if the number of table is huge, and if many of those tables are missing foreign keys

Can you please elaborate? My understanding was that entities always have a 1:1 relationship with tables.

An example would be really helpful.

> entities are fundamentally different from tables

one man’s simplicity is another man’s headache