Ask HN: How do you keep code and database synced up?

Hi all,

I am a new developer, and I was wondering what techniques people use to sync their code and databases. For example, say I edit an entity and add another field to it, I will have to run a corresponding query for the database. As code is at different versions on different machines, how is this managed automatically?

Right now, it's a toy application, and I guess I can just move to a schema-on-read db, (or keep on using the bash script I have), but how is this done in a production environment?