Does an ALTER TABLE modifying several columns lead to several re-calculations of computed columns?

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...)

computed-columns alter-table

asked 14 Jan '11, 14:25

Volker Barth
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alter-table ×12
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question asked: 14 Jan '11, 14:25

question was seen: 2,191 times

last updated: 14 Jan '11, 14:25

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Does an ALTER TABLE modifying several columns lead to several re-calculations of computed columns?

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