Table: tennis_stats_5
Columns: outcome
year
championship
surface
partner
opponents
score

Question: How many opponents have wimbledon (2) as the championship?
SQL: SELECT COUNT("opponents") FROM tennis_stats_5 WHERE "championship" = 'Wimbledon (2)'

Question: What is the surface when the us open is the championship in the year 1979?
SQL: SELECT "surface" FROM tennis_stats_5 WHERE "championship" = 'US Open' AND "year" = 1979