In #datomic is a good pratice pass db as parameter of every function, once the "db" immutable (db/list-users db) But in SQL, what is the good pratice? pass db as parameter? or just define the db value in the namespace? and use (db/list-users)?

I'd say it's same as with everything else; better to pass explicitly as an argument. However, db is often defined as a global variable (e.g. when use #mount)

Other frameworks/libraries like component or integrant encourage passing it as an explicit param.

FWIW if you don’t pass it an an explicit argument, you will have a not good time if you ever realize you need more than one database.

@souenzzo As someone who originally used a global for my db-specs, I can say with absolutely certainty, you're better off passing your db-spec as an argument to every function that may want to do database operations! 😆

Nowadays, we construct the connection pool for each DB "spec" (we have half a dozen different ones in our code now!) in the start of a Database component (Stuart Sierra's Component), and we pass enough of the overall Application Component around the app for everything to be able to get at the various connections as needed

(-> app :database :pooled-db)

(-> app :database :pooled-slave)