About “Unbounded Result Sets”:

There’s no standard SQL syntax to specify result set limits.

Then, examples with the use of TOP, ROWNUM and LIMIT are included.

I think OFFSET/FETCH clause is the ANSI SQL-conformant way to get the first number of rows:

[OFFSET m ROWS] FETCH FIRST n ROWS ONLY

It’s supported by Oracle DB (from Oracle 12c, July 2013), SQL Server, MySQL, and PostgreSQL among others.

TOP, ROWNUM and LIMIT are still supported by some DBMS, however I think they are the old-way.