select
  *
from
  Person
where
  1 = 1
  and CreateDateTime > getdate() - 30
  and case
    when Age > 90 then 1
    when Age < 5 then 0
    when Gender = 'Male' then 1
    when LastName like 'SAM%' then 1
    else 0
  end = 1

A XOR B = (A AND NOT B) OR (NOT A AND B)

-- This is how you would do it if T-SQL had a XOR operator.
SELECT *
FROM user
WHERE (first_name IS NULL) XOR (middle_name IS NULL)

-- This is how you have to code it with AND, OR and NOT operators
SELECT *
FROM user
WHERE (first_name IS NULL AND middle_name IS NOT NULL) 
    OR (first_name IS NOT NULL AND middle_name IS NULL)