ANSI SQL version of SELECT TOP 1

ANSI/ISO SQL:2003 introduced windowing functions:

SELECT * FROM (
  SELECT
    ROW_NUMBER() OVER (ORDER BY age ASC) AS rownum,
    person_id,
    person_name,
    age
  FROM person
) AS foo
WHERE rownum <= 3

Microsoft SQL Server has supported this syntax since SQL Server 2005. http://msdn.microsoft.com/en-us/library/ms189798(v=sql.90).aspx

ANSI/ISO SQL:2008 introduced a simpler syntax for FETCH FIRST, which may be more analogous to Microsoft/Sybase TOP syntax:

SELECT person_id, person_name, age FROM person
FETCH FIRST 3 ROWS ONLY

Microsoft does not yet support this syntax. See also http://en.wikipedia.org/wiki/Select_(SQL)#Limiting_result_rows

If you're still using Microsoft SQL Server 2000, you should read a question I posted a while back about doing "paging" style queries: Emulate MySQL LIMIT clause in Microsoft SQL Server 2000