SQL 涉及的查询问题（我猜是 SUM、Group By、Order by？也许是总计，甚至是计数）

Question

通过SQL查询，找出总交易额最高的Top 5，分别是哪个行业？以及该行业的商店数量？

我的 SQL 数据如下所示：

Store Name	Industry	Transaction Value
Ace	A	196
Ace	A	193
Area	A	168
Apple	A	165
Boy	B	145
Boy	B	143
Bull	B	136
Bread	B	131
Cat	C	116
Cat	C	106
Cake	C	104
Candy	C	102
Dog	D	101
Dog	D	92
Door	D	80
Daddy	D	75
Egg	E	70
Egg	E	67
Earl	E	66
Eagle	E	61

仅供参考，交易额最高的前 5 名是：

No.	Store Name	Industry	Total Transaction Value
1	Ace	A	389
2	Boy	B	288
3	Cat	C	222
4	Dog	D	193
5	Area	A	168

SQL 查询结果应如下所示：

Industry	No. of Stores
A	2
B	1
C	1
D	1
E	0

Answer 1

select a.industry, sum(case when b.name is null then 0 else 1 end) as no 
from
    (select distinct industry from transactions ) a
left join
    (select name, industry 
    from transactions 
    group by name, industry
    order by sum(transaction_vaule) desc limit 5) b
on a.industry = b.industry
group by a.industry
order by a.industry

Answer 2

我想我有一个解决方案。请检查我使用的代码 Common Table Expression ,CASE,SUM and group by =>

WITH CTE AS
(
SELECT industry, SUM(TransactionValue) AS Transaction_Value, 
COUNT(StoreName) AS StoreCount  FROM MYTable
    GROUP BY StoreName,industry
    ORDER BY SUM(TransactionValue) DESC
    Limit 5
)
SELECT T1.industry,
       SUM((CASE WHEN c.industry IS NULL THEN 0
       ELSE 1 END)) as CT
FROM
(SELECT DISTINCT Industry FROM MYTable) AS T1
LEFT JOIN CTE as c ON T1.industry=c.industry
GROUP BY  T1.industry

注意：子查询不是最佳实践，但在您的情况下，我认为不会有性能问题。另外，请检查代码，因为我没有安装 Snowflake SQL 数据库，所以可能会有一些明显的语法错误 .

Answer 3

要获得确定性结果，您必须了解关系。假设前 9 个结果是

Cat/A/600, Dog/A/500, Cat/B/500, Dog/B/400, Cat/C/300, Dog/C/300, Cat/D/300, Dog/D/200, Cat/E/100

哪个是前五名？ Cat/C/300 或 Dog/C/300 或 Cat/D/300？或者其中 none 个？如果我们任意选择一行（按 LIMIT 5 或 FETCH FIRST 5 ROWS ONLY），我们更喜欢一个行业而不是另一个行业。

在标准 SQL 中，我们有子句 FETCH FIRST 5 ROWS WITH TIES，但遗憾的是，snowflake 没有此功能。但是它确实具有 DENSE_RANK。它对我的示例行进行排名：

#1: Cat/A/600
#2: Dog/A/500
#2: Cat/B/500
#3: Dog/B/400
#4: Cat/C/300
#4: Dog/C/300
#4: Cat/D/300
#5: Dog/D/200
#6: Cat/E/100

因为前五个值分别是 600、500、400、300 和 200。

查询：

select industry, count(case when rnk <= 5 then 1 end) as stores
from
(
  select industry, dense_rank() over (order by sum(transaction_value) desc) as rnk
  from mytable
  group by store_name, industry
) ranked
group by industry
order by industry;

如果您只想显示热门行业：

select industry, count(*) as stores
from
(
  select industry, dense_rank() over (order by sum(transaction_value) desc) as rnk
  from mytable
  group by store_name, industry
) ranked
where rnk <= 5
group by industry
order by industry;

SQL 涉及的查询问题（我猜是 SUM、Group By、Order by？也许是总计，甚至是计数）

SQL Query Problem Involving (SUM, Group By, Order by, I guess? and maybe total, or even count)

sql

snowflake-schema

snowflake-cloud-data-platform