MySQL执行子查询报Every derived table must have its own alias问题咨询

你收到的Every derived table must have its own alias报错是MySQL的强制语法要求：所有作为临时表出现在FROM、JOIN子句中的子查询（即派生表），必须显式设置唯一别名，供外层语句引用。
你的SQL中存在两处不符合要求的写法：

• 两个JOIN关联的子查询都没有设置别名
• 外层的SELECT字段、ON关联条件直接引用了子查询内部的表名Game、GamePlaysPlayers，外层查询无法识别子查询内部的表名，只能通过派生表的别名调用字段

select t1.GameID, t1.season as season_2008, t2.season as season_2018, t1.playerID
from (select Game.GameID, Game.season, GamePlaysPlayers.playerID
      from Game 
      inner join GamePlaysPlayers on Game.GameID = GamePlaysPlayers.GameID 
      where Game.season = '20082009'
     ) t1
inner join (
  select Game.GameID, Game.season, GamePlaysPlayers.playerID 
  from Game 
  inner join GamePlaysPlayers on Game.GameID = GamePlaysPlayers.GameID 
  where Game.season = '20182019'
) t2
on t1.GameID = t2.GameID and t1.playerID = t2.playerID;

• 给2008-2009赛季的子查询设置别名t1，2018-2019赛季的子查询设置别名t2，符合派生表的语法要求
• 关联条件改为通过别名t1、t2引用字段，同时增加了playerID的关联，避免相同GameID下不同球员的笛卡尔积问题，不需要关联playerID可自行删除该条件
• 赛季字段增加了别名区分，避免查询结果出现两个重名的season字段

内容的提问来源于stack exchange，提问作者Sindhu