[英]count items in each category
I've the Following Table Schema for table Items 我具有表项目的以下表模式
id | item_id | category_id
I've sample data in this table 我在此表中有示例数据
id | item_id | category_id
1 | 1 | 1
2 | 1 | 2
3 | 2 | 1
4 | 2 | 2
5 | 3 | 1
6 | 1 | 1
Requirement: I need to count all those items which are repeating in each category_id. 要求:我需要计算在每个category_id中重复的所有那些项目。 In the above scenario item_id '1' is repeating in category '1'.
在上述情况下,item_id'1'在类别'1'中重复。 I need to count the invalid or repeating item_id against each category_id.
我需要针对每个category_id计算无效或重复的item_id。
I think this should do it for you: 我认为这应该为您做到:
Select item_Id, category_id
From Table
Group By item_Id, category_id
Having Count(*) > 1
SELECT category_id, item_id, COUNT(*)
FROM table
GROUP BY category_id, item_id
HAVING COUNT(*) > 1
will give you repeating ones. 会给你重复的。 As for 'invalid' you did not define what these are.
至于“无效”,您没有定义这些是什么。
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