-- Get the lowest and highest gdp country in single query
-- UNION operator is used to combine the result-set of two or more SELECT statements.
SELECT * FROM (select top(1) * from world order by gdp desc) a
UNION
SELECT * FROM (select top(1) * from world order by gdp asc) b
country continent area population gdp
0 Afghanistan Asia 647500 31056997 700
3 United States North America 9631420 298444215 37800