Let's say I have a table of people with their names and Dates of Birth.
How can I select all people's names who have greater DofB than another person while only knowing that persons name and not DofB?
You have some options, but I like a JOIN here.
Assuming you have a unique name field (using a unique row identifier like id is probably better):
SELECT p.name FROM person p JOIN person po ON po.name = :name_that_you_know WHERE p.dob > po.dob
This cross JOINs every person row with the row of the person that you named. The results are filter by the date of birth comparison.
Alternatively you can perform the filter in the JOIN condition:
SELECT p.name FROM person p JOIN person po ON po.name = :name_that_you_know AND po.dob < p.dob