Question

我正在使用MySQL。我有两张桌子，我加入了。我需要使用count（a.parent_id）作为countcolumn，所以这个列将被添加到我用select创建的表中。我想知道每个＆＃34; parent_id＆＃34;出现但是根据下面的查询查看包含该列的所有表。该问题是它只返回1条记录，并且它会像所有父级一样计算...

select count(parent_id) as count_column
     , a.parent_id
     , b.job_id
     , a.status as parent
     , b.status as subparent
     , b.description 
from jobs a 
inner join jobs_steps b 
  on  a.id=b.job_id 
where name='XXX' 
  and a.status='FAILED' 
order by a.parent_id desc

如果我在开头删除了计数父ID，则返回78条记录

select a.parent_id
     , b.job_id
     , a.status as parent
     , b.status as subparent
     , b.description 
from jobs a 
inner join jobs_steps b 
  on  a.id=b.job_id 
where name='XXX'
  and a.status='FAILED' 
order by a.parent_id desc

我希望有78条新记录的记录写出每个parent_id出现的数字。

Answer 1

如果你想按照父ID分组你的结果，你应该使用select count(a.parent_id) as count_column , a.parent_id , b.job_id , a.status as parent , b.status as subparent , b.description from jobs a inner join jobs_steps b on a.id=b.job_id where name='XXX' and a.status='FAILED' group by a.parent_id order by a.parent_id desc，但是这不会返回78条记录，因为这些记录不是每个父ID的组，这将返回一条记录每个父ID。我希望这有帮助

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Answer 2

假设您在每个作业中执行了多个步骤（作为每个作业详细信息的重复值）

通常我会使用窗口函数，但由于mySQL不支持它们，请使用查询来计算每个作业的parent_ID数量，然后加入...

select C.JobSteps as count_column
     , a.parent_id
     , b.job_id
     , a.status as parent
     , b.status as subparent
     , b.description 
from jobs a 
inner join jobs_steps b 
  on  a.id=b.job_id
LEFT JOIN (Select count(parent_ID) as JobSteps, job_ID 
            from Job_Steps
            Group by Job_ID) C
 on c.Job_ID = B.Job_ID
where name='XXX' 
  and a.status='FAILED' 
order by a.parent_id desc

这对我来说似乎比在select中使用相关查询的替代方案更快。

select a.parent_id
     , b.job_id
     , a.status as parent
     , b.status as subparent
     , b.description 
     , (Select count(JS.parent_ID) as JobSteps, JS.job_ID 
            from Job_Steps JS
            where a.Id = JS.Job_ID
            Group by Job_ID) C as count_column
from jobs a 
inner join jobs_steps b 
  on  a.id=b.job_id
where name='XXX' 
  and a.status='FAILED' 
order by a.parent_id desc

MYSQL有计数或有计数问题

2 个答案: