查找每个 GROUP BY 结果中的行数
我有一个数据库，可以告诉每个系统当前和新的型号。 （每一行都有系统名称、当前模型和新模型）我需要按当前模型和新模型对结果进行分组。因此，如果当前模型和新模型相同，我想要一个结果。我已经做到了这一点，但我还需要知道每组中有多少个系统。我怎样才能做到这一点？我正在使用 CI
这是我的查询
$query2 = $this->db->query('SELECT * FROM rollout_systems WHERE scope_ID = '.$id.' GROUP BY EAM_Model, new_Model');
（EAM_Model = 当前模型）
不知道我是否澄清得足够多。我需要能够显示当前系统、新系统以及该组中的系统数量。
因此，如果 3 行有“blah”作为当前系统，“blahblah”作为新系统，我想说 当前： 布拉 新：巴拉巴拉 系统数量：3
I have a database the tells each systems current and new model. (Each row has a system name, current model, and new model) I need to group the results by the current model and new model. So if the current and new model are the same i want one result. I got that to work but i also need to know how many systems are in each group. How can I do that? Im using CI
This is my query
$query2 = $this->db->query('SELECT * FROM rollout_systems WHERE scope_ID = '.$id.' GROUP BY EAM_Model, new_Model');
(EAM_Model = current model)
Don't know if i clarified enough. I need to be able to display the Current System, the New System, and the number of systems in that group.
So if 3 rows have "blah" as there current system and "blahblah" as there new system, i want it to say
Current: Blah
New: Blah Blah
number of systems: 3
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在同一个语句中执行 select * 和 group by 是没有意义的。您分组所依据的列需要位于您的选择中，但您的选择中应该有一个聚合函数，例如 count(*) 。我不确定我完全理解你想要做什么，但我认为你想要类似的东西：
It doesn't make sense to do a select * and a group by in the same statement. The columns you group by need to be in your select but then you should have an aggregate function like count(*) in your select. I'm not sure I totally understand what you are trying to do, but I think you want something like:
如果您只需要项目数量，请使用 SELECT EAM_Model, new_Model, COUNT(*) FROM ...等。对查询进行分组时，您通常希望执行 COUNT 或 SUM 等聚合否则对数据进行分组就没有意义。
If you just want the number of items, use
SELECT EAM_Model, new_Model, COUNT(*) FROM... etc. When you group a query, you normally want to be performing an aggregate like COUNT or SUM or else it doesn't make sense to be grouping the data.$query2 = $this->db->query('SELECT count(*) FROM rollout_systems WHERE range_ID = '.$id.' GROUP BY EAM_Model, new_Model');
你要求的是这个吗？
$query2 = $this->db->query('SELECT count(*) FROM rollout_systems WHERE scope_ID = '.$id.' GROUP BY EAM_Model, new_Model');
Is it this you are asking for?