group by 取每组最大时间的值

表数据

第一种:

SELECT * FROM (SELECT * FROM clinic HAVING 1 ORDER BY created_time DESC) c GROUP BY c.unified_social_credit_code

注意： having 1 不能少， 不知道原理， 或者 在 order by 后面加 limit 100000 也可以

第二种

SELECT * FROM clinic c WHERE c.id IN (SELECT SUBSTRING_INDEX(GROUP_CONCAT(id ORDER BY created_time DESC), ‘,’, 1) FROM clinic GROUP BY unified_social_credit_code)

亲测可行；

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第三种（失败）

SELECT * FROM clinic c GROUP BY c.unified_social_credit_code HAVING c.created_time = MAX(c.created_time)

得到结果


求解释下，什么原因呢