过滤不带子查询的值

Question

如果用户多次填写调查问卷，我将尝试仅获取最新调查日期的值。

但是，由于响应表很大，因此我宁愿不在where子句的子查询中这样做

select *
from responses r1
where r1.survey_date = (select MAX(survey_date) from responses r2 where
r1.user_id = r2.user_id);

这是加载数据的示例 https://www.db-fiddle.com/f/chUhe2HjoAa9QRNmp5pfSv/3

Answer 1

此查询应该可以：

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</p>

您只需要在select * from responses r1 where r1.survey_date = (select MAX(survey_date) from responses r2 where r1.user_id = r2.user_id); 上建立索引。