Well personally I favour event sourcing and so in my systems the SQL database (if there is one) is only written to by the event rollup component. But even if you're not that extreme you probably want to have some clear structure to where your database writes happen rather than randomly writing it from any arbitrary line of code. The important thing is to have a structure that everyone working on the code understands so that you all know where any write to the database must have come from, not the specifics of what that structure is.
