Can you swap two values in SQL in one statement?

For instance, if I have records with an "order" value, and want to swap six and five around so that six becomes five and five becomes six, can I do it in one statement?

I'm not in a position to test this at the moment.

I was thinking you'd have to temporarily set the "order" value five to null, or a million or something, then make six into five and the temporarily-changed record into six.

Because if you do it like this:

set order = 5 where order = 6
set order = 6 where order = 5
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then you're just going to end up with two sixes, aren't you? And if you do "limit =1" then you don't know which one you're going to get.