Join条件下的BigQuery子查询

Question

您好，我正在将一些TSQL查询转换为BigQuery标准SQL，并在转换JOIN条件时遇到了子查询，请提供帮助，谢谢。]

TSQL

select * From Table1 t1
left join Table3 t2 
  on t2.userid=t1.userid 
    and t2.id in (select min(id) From Table3 t3 where t3.userid=t2.userid)
where t1.creationdate > <date condition> 
似乎，BigQuery在WHERE或JOIN条件下将不直接支持子查询。那么，有没有一种方法可以在BigQuery中实现相同目标？ 

[您好，我正在将一些TSQL查询转换为BigQuery标准SQL，并在转换JOIN条件时遇到了子查询，请感谢您能否为TSQL选择* ...]提供帮助，请感谢

Answer 1

您应该可以：

select * From Table1 t1
left join 
  (Table3 
     join (select min(id) min_id, userid From Table3 t3 group by userid) t3_min_id 
     on Table3.id = t3_min_id.min_id 
       AND Table3.userid = t3_min_id.userid) t2
on t2.userid=t1.userid 
where t1.creationdate > <date condition>