RDBMSを指定しないので、ここではMySQLにあります
DELETE teammembers FROM teammembers
JOIN teams on teammembers.teamId = teams.teamId
WHERE teams.eventId = 1
RDBMSを指定しないので、ここではMySQLにあります
DELETE teammembers FROM teammembers
JOIN teams on teammembers.teamId = teams.teamId
WHERE teams.eventId = 1