INSERT INTO wp_postmeta (post_id, meta_key, meta_value)
SELECT post_id, 'amazonS3_info' as meta_key, CONCAT('a:2:{s:6:"bucket";s:7:"bucketname";s:3:"key";s:', CHAR_LENGTH(meta_value) + 19,':"wp-content/uploads/', meta_value, '";}') FROM wp_postmeta WHERE meta_key = '_wp_attached_file'

INSERT INTO wp_postmeta (post_id, meta_key, meta_value)
SELECT post_id, 'new_url' as meta_key, CONCAT('a:2:{s:6:"bucket";s:7:"bucketname";s:3:"key";s:', CHAR_LENGTH(meta_value),':"', meta_value, '";}') from wp_postmeta WHERE meta_key = '_wp_attached_file'

INSERT INTO wp_postmeta (post_id, meta_key, meta_value)
SELECT post_id, 'new_url' as meta_key, CONCAT('a:2:{s:6:"bucket";s:7:"crewtoo";s:3:"key";s:', CHAR_LENGTH(meta_value),':"', meta_value, '";}') from wp_postmeta WHERE meta_key = '_wp_attached_file'

INSERT INTO wp_postmeta2 (post_id, meta_key, meta_value)
SELECT post_id, 'new_url' as meta_key, CONCAT('a:2:{s:6:"bucket";s:7:"crewtoo";s:3:"key";s:', CHAR_LENGTH(meta_value),':"', meta_value, '";}') from wp_postmeta2 WHERE meta_key = '_wp_attached_file'

INSERT INTO wp_postmeta2 (post_id, meta_key, meta_value)
SELECT post_id, 'new_url' as meta_key, CONCAT('{', meta_value, '}') from wp_postmeta2 WHERE meta_key = '_wp_attached_file'

For use with AWS S3 Wordpress pluign

Duplicate MySQL rows with slight changes

MySQL