Question

我在UNION中遇到ORDER BY RAND（）的问题。它似乎没有在UNION内的单独查询中随机排序。

我只想订购子查询而不立即对整个查询进行排序，因为订单需要是Subquery 1＆gt; subquery2＆gt; subquery3。

我已尝试过一些其他随机函数用于MySQL，如NEWID（）和UUID（），但它们似乎也无法正常工作。

我使用WordPress获取结果。

SELECT *
        FROM (
                (SELECT act.wordpress_id,
                        act.title,
                        act.main_image,
                        loc.id,
                        "activities" AS type,
                        loc.town,
                        loc.village
                FROM tha_wc_activity act
                INNER JOIN tha_wc_location loc
                ON act.location_id = loc.id
                WHERE
                  act.active = 1 AND
                  act.visible_in_activities_overview = 1 AND
                  loc.id = 1
                ORDER BY RAND()
                )
            UNION
                (SELECT act.wordpress_id,
                        act.title,
                        act.main_image,
                        loc.id,
                        "activities" AS type,
                        loc.town,
                        loc.village
                FROM tha_wc_activity act
                INNER JOIN tha_wc_location loc
                ON act.location_id = loc.id
                WHERE
                  act.active = 1 AND
                  act.visible_in_activities_overview = 1 AND
                  loc.village = "villageName"
                ORDER BY RAND()
                )
            UNION
                (SELECT act.wordpress_id,
                        act.title,
                        act.main_image,
                        loc.id,
                        "activities" AS type,
                        loc.town,
                        loc.village
                FROM tha_wc_activity act
                INNER JOIN tha_wc_location loc
                ON act.location_id = loc.id
                WHERE
                  act.active = 1 AND
                  act.visible_in_activities_overview = 1 AND
                  loc.town = "townName"
                ORDER BY RAND()
                )
            ) AS act
            WHERE act.wordpress_id != 1
            LIMIT 0, 15)

更新感谢Gordon Linoff，我发现我必须限制单独的子查询，否则它不会得到有序的结果

Answer 1

我不太清楚你的问题是什么。您在子查询中使用order by rand()，但随后选择了所有结果。获取所有行是所有行，无论它们的顺序如何。

然后，您正在使用union来删除重复项，并且还有其他逻辑。

据推测，你想要这样的东西：

select *
from (<subquery 1>
      union
      <subquery 2>
      . . .
     ) t
where . . .
order by rand()
limit 15;

除非您使用limit。

，否则无需订购子查询

请注意，您可能希望使用union all而不是union - 除非您明确希望产生删除重复项的开销。

ORDER BY RAND（）不在UNION中工作

1 个答案: