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【DM版本】: 8
【操作系统】：linux
【CPU】:
【问题描述】*：数据库左联分组查询sql脚本如下：

select count(1)
from (select
r."id", max(rr.fire_danger_rating)
from "oyz_hubei_commanddispatch_dm"."oyz_region" r
LEFT join "oyz_hubei_commanddispatch_dm"."oyz_grid_region" ogr
on r.id = ogr.region_id
left join "oyz_hubei_commanddispatch_dm"."oyz_warning_grid_ffmc_level_predict" rr
on ogr.grid_id=rr.grid_id
group by r.id );

oyz_region 表只有 1591条，此sql却得到了三百多万数据。

按照下面写法却是 1591条：

select count(1)
from (select
r."id", max(rr.fire_danger_rating)
from "oyz_hubei_commanddispatch_dm"."oyz_region" r
LEFT join "oyz_hubei_commanddispatch_dm"."oyz_grid_region" ogr
on r.id = ogr.region_id
left join "oyz_hubei_commanddispatch_dm"."oyz_warning_grid_ffmc_level_predict" rr
on ogr.grid_id=rr.grid_id
group by r.id ,ogr."region_id");

下面的写法：count(1) 得到的结果是三百多万，但是如果点 DM管理工具的所有数据，看到的数据却是1591行：

select count(1)
from (select
r."id", max(rr.fire_danger_rating)
from "oyz_hubei_commanddispatch_dm"."oyz_region" r
LEFT join "oyz_hubei_commanddispatch_dm"."oyz_grid_region" ogr
on r.id = ogr.region_id
left join "oyz_hubei_commanddispatch_dm"."oyz_warning_grid_ffmc_level_predict" rr
on ogr.grid_id=rr.grid_id
group by r.id ORDER by r."id" asc);