According to the docs - and as discussed here - , an ALTER TABLE that changes the datatype of a column will enforce a re-calculation of all computed columns of that table.
I would usually try to put several modifications like changing several columns in one single ALTER TABLE statement.
What implications does that have for the re-calculation:
- Will this trigger only one single re-calculation (i.e. the changes are made then one re-calculation takes place)?
- Or will each alteration trigger a separate run, possibly causing several rewrites of the same row?
- And what if among other modifications, the datatype of a computed column is altered, too? Does this lead to another re-calculation?
(In my current case, the re-calculation won't change the contents, and as such it's merely a question of performance; however, in other circumstances it might matter more...)
14 Jan '11, 14:25