MySQL 5.6

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Records: 2  Duplicates: 0  Warnings: 0

Records: 4  Duplicates: 0  Warnings: 0

id	name	surname	dob	email	telephone
10	Steve	Bobbly	1970-01-01	uvw@xyz.com	123456789
15	James	Bond	1950-01-01	007@bond.com	101010999

id	entity_id	property	old_value	new_value
1	10	name	John	Bob
2	10	email	abc@def.com	uvw@xyz.com
3	10	telephone	null	0123456789
4	10	name	Bob	Steve

SELECT id, name, surname, dob, email, telephone
FROM customer
UNION ALL
SELECT
  CONCAT(entity_id, '_1') AS id,
  COALESCE(SUBSTRING_INDEX(GROUP_CONCAT(CASE WHEN property = 'name' THEN COALESCE(old_value, '') END ORDER BY a.id SEPARATOR '@@'), '@@', 1), c.name) AS name,
  COALESCE(SUBSTRING_INDEX(GROUP_CONCAT(CASE WHEN property = 'surname' THEN COALESCE(old_value, '') END ORDER BY a.id SEPARATOR '@@'), '@@', 1), c.surname) AS surname,
  COALESCE(SUBSTRING_INDEX(GROUP_CONCAT(CASE WHEN property = 'dob' THEN COALESCE(old_value, '') END ORDER BY a.id SEPARATOR '@@'), '@@', 1), c.dob) AS dob,
  COALESCE(SUBSTRING_INDEX(GROUP_CONCAT(CASE WHEN property = 'email' THEN COALESCE(old_value, '') END ORDER BY a.id SEPARATOR '@@'), '@@', 1), c.email) AS email,
  COALESCE(SUBSTRING_INDEX(GROUP_CONCAT(CASE WHEN property = 'telephone' THEN COALESCE(old_value, '') END ORDER BY a.id SEPARATOR '@@'), '@@', 1), c.telephone) AS telephone
FROM audit_log a
JOIN customer c ON c.id = a.entity_id
GROUP BY entity_id

id	name	surname	dob	email	telephone
10	Steve	Bobbly	1970-01-01	uvw@xyz.com	123456789
15	James	Bond	1950-01-01	007@bond.com	101010999
10_1	John	Bobbly	1970-01-01	abc@def.com