SQL Server Count on a grouped by

Question

我有3张 table 。我想按 item.name 分组并计算它可以在 idetail 中找到的次数。此查询仅计算所有行，而不是按行分组。

有谁知道如何修复它？

SELECT i.name, COUNT(i.name)
FROM item AS i
INNER JOIN item_category AS ic ON i.i_category_id = ic.ic_id
INNER JOIN idetail AS id ON ic.ic_id = id.id_category_id
WHERE ic.ic_id = 1002
GROUP BY i.name

Answer 1

这就是你想要的:

select x.name
     , count(*) as cntNames
     , sum(x.cntDetails) as cntDetails
  from (
        SELECT i.name, COUNT(*) as cntDetails
          FROM item AS i
         INNER JOIN item_category AS ic ON i.i_category_id = ic.ic_id
         INNER JOIN idetail AS id ON ic.ic_id = id.id_category_id
         WHERE ic.ic_id = 1002
          -- NOTICE THE 2nd Value in the group by!
         GROUP BY i.name,id.id_category_id
       ) x
  group by name