sql - PostgreSQL distinct on, group by, having in one？

Question

我在使用 PostgreSQL 查询时遇到了一些问题

我想要的是一个“广告系列”列表，按距离排序，并且在距某个位置 [in_lat, in_lng, in_radius] 的最小距离内 现在，我正在检索距离(使用 distance_in_km(...) )两次。一次用于订购，一次用于检查事件是否在我的首选半径内。

此外，一个事件可能有多个“Campaignreceiver”条目(接收类型 [EMAIL、WEBSITE 等...])

我只想检索一次事件。因此 DISTINCT ON。

所以问题是，我怎样才能让“WHERE distance < in_radius”这样的时间起作用。 我的猜测是添加一个 GROUP BY 和 HAVING，但我做了一些测试但没有成功。

非常感谢任何帮助!!!

    SELECT DISTINCT ON (c.campaign_uuid, distance)
            c.campaign_uuid,
            prl.lat,
            prl.long,
            distance_in_km(prl.lat, prl.long, in_lat, in_lng) AS distance                
        FROM 
            usercampaignrelations AS ucr
        LEFT JOIN
            campaignreceivers AS cr
        ON
            ucr.usercampaign_uuid = cr.usercampaign_uuid
        LEFT JOIN
            campaigntargetgrouprelations AS ctg
        ON
            cr.campaigntargetgroup_uuid = ctg.campaigntargetgroup_uuid
        LEFT JOIN
            campaigns AS c
        ON
            ucr.campaign_uuid = c.campaign_uuid
        LEFT JOIN
            companycampaignrelations AS cc
        ON
            c.campaign_uuid = cc.campaign_uuid
        LEFT JOIN
            pointradiuslocations AS prl
        ON
            c.location_uuid = prl.location_uuid
        WHERE 
            ucr.user_uuid = in_user_uuid
        AND
            (cr.status = 'SENT' OR cr.status = 'RETRIEVED')
        AND
            distance_in_km(prl.lat, prl.long, in_latitude, in_longtitude) < in_radius
        ORDER BY
            distance
        LIMIT 
            in_limit

Answer 1

AFAIK，distance_in_km() 只会被调用一次(每行)，只要您将它与相同的参数一起使用，因此 WHERE 和 ORDER BY 将不会再次评估它。