ALTER TABLE my_contacts ADD COLUMN interests1 VARCHAR(50),
ADD COLUMN interests2 VARCHAR(50),
ADD COLUMN interests3 VARCHAR(50),
ADD COLUMN interests4 VARCHAR(50);
UPDATE my_contacts SET interests1 = SUBSTRING_INDEX(interests,',',1);
UPDATE my_contacts SET interests = SUBSTR(interests, LENGTH(interests1)/2 + 3, (LENGTH(interests) - LENGTH(interests1))/2);
UPDATE my_contacts SET interests2 = SUBSTRING_INDEX(interests,',',1);
UPDATE my_contacts SET interests = SUBSTR(interests, LENGTH(interests2)/2 + 3, (LENGTH(interests) - LENGTH(interests2))/2);
UPDATE my_contacts SET interests3 = SUBSTRING_INDEX(interests,',',1);
UPDATE my_contacts SET interests = SUBSTR(interests, LENGTH(interests3)/2 + 3, (LENGTH(interests) - LENGTH(interests3))/2);
и так далее
...
ALTER TABLE my_contacts DROP COLUMN interests