How is uid related to entity_id in Profile2 in Drupal?

Question

PHP

There is no direct relational relationship between the field_* tables and users. How is uid related to entity_id in Profile2 in Drupal? You need to check the values ​​of the user profile fields.
Actually I want to understand not only the API, but also how the data is stored.

Answer 1

The answer concerns Drupal 7.
If we talk about the Profile2 module, then the uid is stored there in the profile table, the uid column.
cgit.drupalcode.org/profile2/tree/profile2.install
And if the question is how the uid and entity_id are connected, then the connection occurs through the table of a specific entity.
For example, the node entity in the table node.uid
cgit.drupalcode.org/drupal/tree/modules/node/node....
In turn, user is also an entity.
Fields are bound to entities. Therefore, in the case of nodes field -> node -> uid.
You open a specific module and look at module.install, it usually describes the structure of tables in the schema api format.