Actually, when working with Alter table (and not using the visual editors), I don't think there should be any data migration. In SQL Server, for instance, when you are changing an existing table using the visual editor built into SSMS, it might sometime migrate the data to a temporary location, drop the table, re-create it with the changes needed, and move the data into the newly formed copy of the table. However, when using the query editor to write Alter table statements, I'm not aware of such a process (that doesn't mean it doesn't happen - it could very well be that the query optimizer decides it's better to drop and recreate the table instead of simply altering it).
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Adding a new column to an existing table doesn't force migrating the data. I don't know where you've got that information from but it's simply wrong.
sure.
However, changing schemas does, which was really the core take away 🙃
That depends on what you mean exactly by changing schema...
interesting,
I currently only know that any change to the schema => migration
how does the type of schema change influence migration? What are some of the different type of changes?
Actually, when working with Alter table (and not using the visual editors), I don't think there should be any data migration. In SQL Server, for instance, when you are changing an existing table using the visual editor built into SSMS, it might sometime migrate the data to a temporary location, drop the table, re-create it with the changes needed, and move the data into the newly formed copy of the table. However, when using the query editor to write Alter table statements, I'm not aware of such a process (that doesn't mean it doesn't happen - it could very well be that the query optimizer decides it's better to drop and recreate the table instead of simply altering it).