Prioritizing a set by using union operator

Question

My requirement is to print data whose log_in_id starts with a and end with y first, then to print data starting with a and b.
select * from userid where log_in_id like 'a%y' union select * from userid where log_in_id like 'a%' or log_in_id like 'b%'

Answer 1

Why go through the table twice? I would do something like:
SQL> SELECT log_in_id
  2  FROM (SELECT 'bob' log_in_id FROM dual
  3        UNION ALL
  4        SELECT 'bill' from dual
  5        UNION ALL
  6        SELECT 'ally' from dual
  7        UNION ALL
  8        SELECT 'abby' from dual
  9        UNION ALL
10        SELECT 'allen' from dual
11        UNION ALL
12        SELECT 'albert' from dual)
13  ORDER BY CASE WHEN log_in_id LIKE 'a%y' THEN 1 ELSE 2 END,
14           log_in_id;
LOG_IN
abby
ally
albert
allen
bill
bobHTH
John