In Active Record, when we deal with migrations, what exactly is moving? When I think of migrations, I think of something moving from point A to point B like the common meaning in English. I haven't been able to see what is moving in my research.
Migrations: What is actually moving from point A to point B in migrations?
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A migration in the context of database migrations is more of an abstract concept than data being "moved" around. In a database migration, we conceptualize the database being in state A and "migrating" to state B.
Take for example, when we add a new field to a table. The table during state A is:
When we add the field, data is not being literally moved, but we can conceptualize that the data is "moving" or "migrating" from the above state A to the new table state of B: