关于 left join 多张表后, order by 效率陡然下降,如何优化?? - V2EX
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JarvisRay
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关于 left join 多张表后, order by 效率陡然下降,如何优化??

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  •   JarvisRay 2020-08-25 10:53:28 +08:00 2471 次点击
    这是一个创建于 1877 天前的主题,其中的信息可能已经有所发展或是发生改变。

    已经很多次碰到这种情况了,一直得不到很好的解决方案,写个帖子问问。

    SELECT DISTINCT p.id, p.channel_id, o.channel_name, d.drug_manufacturer, p.patient_name, p.patient_gender, p.patient_age, p.patient_tel, p.diagnostic_name AS diagnosis, p.doctor_name, p.review_doctor_name AS pharmacist_name, p.pharmacist_name AS config_pharmacist_name, p.STATUS, p.review_time, p.rp_id, p.rp_url, p.refuce_reason, p.total_price, p.add_time FROM prescription_in_channel p, org_channel o, drug_in_channel d WHERE p.id = d.pre_id AND o.id = p.channel_id ORDER BY p.add_time DESC limit 1,10

    上述语句中,没加 order by 目前是 0.2s 左右的时间,加了之后,变为 1.5s 。后期业务数据会逐步变多,我想到时候肯定就特慢了。 不知道有没有什么好的解决方案?

    5 条回复    2020-09-06 18:32:09 +08:00
    des
        1
    des  
       2020-08-25 10:54:53 +08:00
    先上个 explain 吧
    weirdo
        2
    weirdo  
       2020-08-25 10:58:18 +08:00
    ....你这没有 left join 啊。。
    JarvisRay
        3
    JarvisRay  
    OP
       2020-08-25 11:01:21 +08:00
    @weirdo 不好意思。。。。。。。。我重新发帖,擦,语句搞错了
    zshneedmoney
        4
    zshneedmoney  
       2020-08-25 11:04:35 +08:00
    join (select add_time fromprescription_in_channel ordrr by add_time DESC ) 别名 on p.add_time = 别名
    zhz1237ok
        5
    zhz1237ok  
       2020-09-06 18:32:09 +08:00
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