In this post, Adron discusses primary keys and their types in relational databases. He explains the different kinds of primary keys a table can have, including super key, candidate key, alternate key, compound key, composite key, and surrogate key. Additionally, he provides two videos related to specific primary keys: UUIDs & creating Short URL Safe UUIDs. Furthermore, Adron talks about character data and numeric data types in GraphQL and how they map back against Postgres types. He also shares a reference grid that maps Postgres types to their respective API types in Hasura served GraphQL JSON result objects.