user_id | meta_key | meta_value
       1|Name      |David
       1|Lastname  |Brown

user_id|Name |Lastname
      1|David|Brown

select m1.user_id, m1.meta_value as Vorname_M, m2.meta_value as Nachname_M,m3.meta_value as Adresse_M
from wp_usermeta m1
join wp_usermeta m2 on (m1.user_id = m2.user_id and m2.meta_key =  'nachname')
join wp_usermeta m3 on (m2.user_id = m3.user_id and m3.meta_key = 'adress')
where m1.meta_key = 'vorname'