CREATE TABLE team (team_id_br VARCHAR2, name VARCHAR2)
CREATE TABLE salary (salary NUMBER, team_id VARCHAR2)

What is average salary of the players in the team named 'Boston Red Stockings' ?
SELECT AVG(T1.salary) FROM salary AS T1 JOIN team AS T2 ON T1.team_id = T2.team_id_br WHERE T2.name = 'Boston Red Stockings'
SELECT AVG("T1"."salary") FROM "salary" "T1" JOIN "team" "T2" ON "T1"."team_id" = "T2"."team_id_br" AND "T2"."name" = 'Boston Red Stockings'