Question about SQL and performance

Hi
Is there any better performance in SQL query if i add below lines to my SQL
statement, suppose i know that my sql will return a maximum of 40 rows, is
there any advantage of adding these lines, i can understand adding these
lines if the SQL result may be 500 rows then this will bring only first 50
rows and thus save getting extra data,

Any ideas or thoughts on adding these lines to SQL


FETCH FIRST 50 ROWS ONLY
OPTIMIZE FOR 2 ROWS
FOR READ ONLY
WITH NC;