PreparedStatement vs. Statement problem

[yoursoft <yoursoft(at)freemail(dot)hu>]

I have a problem:
SELECT * FROM mytable WHERE c1 like 'a' UNION ALL SELECT * FROM mytable 
WHERE c2 like 'a' || '%' AND c2 not like 'a' UNION ALL SELECT * FROM 
mytable WHERE c2 like '%' || 'a' || '%' AND c2 not like 'a' || '%' AND 
c2 not like 'a' LIMIT 101 OFFSET 0

Where 'a' is a variable.
When I run this query from Statement. There is no problem. The result is 
ordered by: First SELECT, second SELECT third SELECT.
When I run this query from PreparedStatement ('a' values replaced by ?). 
The result is ordered by in alphabets.Why?

Regards,
   Ferenc