title: SQL Loop over a family tree
body: <p>Using SQL server 2008.
  I have a family tree of animals stored in a table, and want to give some information on how 'genetically diverse' (or not) the offspring is.
  In SQL how can I produce sensible metrics to show how closely related the parents are?
  Perhaps some sort of percentage of shared blood, or a number of generations to go back before there is a shared ancestor?</p>
  
  <pre><code>AnimalTable 
  Id
  Name
  mumId
  dadId
  
  select * from AnimalTable child
  inner join AnimalTable mum on child.[mumId] = mum.[Id]
  inner join AnimalTable dad on child.[dadId] = dad.[Id]
  
  inner join AnimalTable mums_mum on mum.[mumId] = mums_mum.[Id]
  inner join AnimalTable mums_dad on mum.[dadId] = mums_dad.[Id]
  
  inner join AnimalTable dads_mum on dad.[mumId] = dads_mum.[Id]
  inner join AnimalTable dads_dad on dad.[dadId] = dads_dad.[Id]
  </code></pre>