Given a discrete function...

if they ask you to find the domain and range, lets say.... 

x | 1 | 9 | 6 | 3 |
y | 2 | 4 | 6 | 8 | 

this is a table btw

would we have to write the domain and range in numerical order? 
also does this only apply to tables or discrete function graphs too? 

so like would the domain be {1,3,6,9} 
and range {2,4,6,8}

Thank you sm! :)