MySQL最大日期查询

我需要找到证书的最长日期才能将存档字段设置为0。问题在于并非所有的认证都有有效期。现有的更新查询如下所示：

update user_certs uc1
    join ( select user_id, cert_id, ifnull(max(date_expire),max(cert_date)) cert_date
        from user_certs
    group by user_id,cert_id ) uc2 on (uc1.user_id=uc2.user_id and uc1.cert_id=uc2.cert_id and ifnull(uc1.date_expire,uc1.cert_date)=uc2.cert_date)
    set uc1.archive=0

update user_certs uc1
    join ( select user_id, cert_id, c.expiration, max(case when date_expire > cert_date + interval c.expiration month then date_expire else cert_date end ) cert_date
        from user_certs
        join certifications c on c.id = cert_id
    group by user_id,cert_id ) uc2 on (uc1.user_id=uc2.user_id and uc1.cert_id=uc2.cert_id and (case when uc1.date_expire > uc1.cert_date + interval uc2.expiration month then uc1.date_expire else uc1.cert_date end) = uc2.cert_date)
    set uc1.archive=0;

在某些情况下，查询不考虑同一证书的多个条目。其中一个可能有一个到期日期，但其他可能有一个较新的证书日期，但到期日期为空，因为记录尚未从权威数据库导入

下面的查询将解释该条件，但我无法使其正常工作。即使我将c.expiration值硬编码为36而不是加入，它也会不断返回一个无效使用组函数错误

update user_certs uc1
    join ( select user_id, cert_id, max(case when date_expire > cert_date + interval c.expiration month then date_expire else cert_date end ) cert_date
        from user_certs
        join certifications c on c.id = cert_id
    group by user_id,cert_id ) uc2 on (uc1.user_id=uc2.user_id and uc1.cert_id=uc2.cert_id and max(case when uc1.date_expire > uc1.cert_date + interval uc2.expiration month then uc1.date_expire else uc1.cert_date end )=uc2.cert_date)
    set uc1.archive = 0;

因此，我需要根据到期日期或证书日期+证书到期（c.到期）中的较大者（以月为单位）查找最新的证书

更新：

在Jim MC的评论帮助下解决。更正的查询如下：

update user_certs uc1
    join ( select user_id, cert_id, ifnull(max(date_expire),max(cert_date)) cert_date
        from user_certs
    group by user_id,cert_id ) uc2 on (uc1.user_id=uc2.user_id and uc1.cert_id=uc2.cert_id and ifnull(uc1.date_expire,uc1.cert_date)=uc2.cert_date)
    set uc1.archive=0

update user_certs uc1
    join ( select user_id, cert_id, c.expiration, max(case when date_expire > cert_date + interval c.expiration month then date_expire else cert_date end ) cert_date
        from user_certs
        join certifications c on c.id = cert_id
    group by user_id,cert_id ) uc2 on (uc1.user_id=uc2.user_id and uc1.cert_id=uc2.cert_id and (case when uc1.date_expire > uc1.cert_date + interval uc2.expiration month then uc1.date_expire else uc1.cert_date end) = uc2.cert_date)
    set uc1.archive=0;

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我不是这样问这个问题的。你的语法错误是由于在ON子句中使用MAX（它抱怨的组函数）引起的。麦克斯在那里说不通。谢谢@JimMc！把它弄明白并发布了工作查询。