In a scenario where you have a computed column in a table it is best to keep all the column from where the value is being computed for this computed column in that same table.
You can have computed column whos value is being computed from columns from other tables but than you have to create INSTEAD OF INSERT triggers, AFTER UPDATE, AFTER DELETE
triggers on all tables from where the value is being computed to sync the computed column for any changes in the source table, which can be a hell of task and Triggers can be silent killers at times.
So to avoid all this hassle just keep the columns from where the values are being computed and the computed column it self in One table.
Another even simpler option will be to create another view
which gathers data at run time from these multiple underlying tables and compute them at runtime for you. Since you already have the data in you database from where this column is being computed its better to compute them at runtime only when you want to see the computed results.
If you have lots of data in your underlying tables and computing them values at run time takes a lot of time then consider INDEXED VIEWS
.
My suggestion would be avoid as much as possible to have a situation where you have a computed column and source columns in multiple tables.