Table: west_ham_2008_09
Columns: match
date
competition_or_tour
ground
opponent
score1

Question: What ground had Portsmouth reserves as an opponent?
SQL: SELECT "ground" FROM west_ham_2008_09 WHERE "opponent" = 'portsmouth reserves'

Question: What ground had a match smaller than 6 and Chelsea Reserves as the opponent?
SQL: SELECT "ground" FROM west_ham_2008_09 WHERE "match" < 6 AND "opponent" = 'chelsea reserves'