Top 10 spillere med det højeste slaggennemsnit

fordi du fra din underforespørgsel (resultat af forening) kun returnerer kolonnen "Batsman_". du skal genindstille alle de kolonner, du har brug for :

select Batsman_, sum(batsman_runs)/count(player_dismissed) as Average 
from
(
 (select batsman as Batsman_,batsman_runs,player_dismissed from IPL_BALL_BY_BALL) 
 union all 
 (select non_striker as Batsman_,batsman_runs,player_dismissed from IPL_BALL_BY_BALL)
)
group by Batsman_ 
order by Average desc;