sql - レコードの値を交換する方法は?

Question

role = 1to value を持つすべてのレコードとto valueを2持つレコードを更新する方法は?role = 21

  login   | role
----------+------
 john     |    1
 anne     |    2
 adam     |    1
 robert   |    1
 katie    |    1
 bob      |    2
 tom      |    2
 ...many records with 1 and 2 values

Answer 1

UPDATE table

SET role = CASE role
               WHEN 1 THEN 2
               ELSE 1
           END

WHERE role = 1 OR role = 2;

Answer 2

UPDATE [table]
SET role = CASE role
               WHEN 1 THEN 2
               ELSE 1
           END
WHERE role = 1 OR role = 2;