What is average salary of the players in the team named 'Boston Red Stockings' ?
CREATE TABLE salary (salary INTEGER, team_id VARCHAR); CREATE TABLE team (team_id_br VARCHAR, name VARCHAR)
[SQL] 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' [/SQL]