如果行不存在，则mysql左连接，使用0

我试图获得具有平均参与率的表的日期列表。但目前它正在略过列表中的日期，如果它们不存在于媒体表中。因此，如果该行存在的犯规，我想参与度为0如果行不存在，则mysql左连接，使用0

例如（目前）

2017-09-30 - 123 
2017-09-28 - 1234 
2017-09-27 - 12345

等

，但它应该是

2017-09-30 - 123 
2017-09-29 - 0 
2017-09-28 - 1234 
2017-09-27 - 12345

这里是我的查询

"select d.date AS created_at, 
       AVG((IFNULL(v.likes, 0) + IFNULL(v.comments, 0))/
       IFNULL((SELECT count FROM followers prev WHERE DATE(prev.created_at) = DATE(v.created_at) 
                AND prev.profile_id = '".$this->profile->id."' 
                ORDER BY created_at 
                DESC LIMIT 1), 0) * 100) 
                AS count 
       from 
       (select adddate('1970-01-01',t4.i*10000 + t3.i*1000 + t2.i*100 + t1.i*10 + t0.i) date from 
       (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t0, 
       (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t1, 
       (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t2, 
       (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t3, 
       (select 0 i union select 1 union select 2 union select 3 union select 4 union select 5 union select 6 union select 7 union select 8 union select 9) t4) d 
       left join media v on d.date = DATE(v.created_at) 
       where d.date between '".Carbon::createFromFormat('Y-m-d', $this->startDate)->toDateTimeString()."' and '".Carbon::createFromFormat('Y-m-d', $this->endDate)->toDateTimeString()."' 
       AND v.profile_id = '".$this->profile->id."' 
       group by d.date 
       order by d.date DESC"

来源

2017-10-05 Dan

这不是一个查询，这是一个字符串。 – HoneyBadger

以及即时通讯使用laravel，但我并不想要全部粘贴 – Dan

认真考虑处理应用程序代码 – Strawberry

要获得真正的LEFT JOIN结果，将表V的条件从WHERE到ON条款：

 left join media v on d.date = DATE(v.created_at) AND v.profile_id = '".$this->profile->id."' 
     where d.date between '".Carbon::createFromFormat('Y-m-d', $this->startDate)->toDateTimeString()."' and '".Carbon::createFromFormat('Y-m-d', $this->endDate)->toDateTimeString()."'

来源

2017-10-05 08:45:53 jarlh

非常感谢！我以为你只能在WHERE子句中使用AND – Dan

如果行不存在，则mysql左连接，使用0

回答

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