php - 如何从Mysql中基于总销售额的每个用户名3表中获取每个数据

Question

我尝试从 3 个表中获取数据，即:“artist”、“sales”、“claim”

所以我想尝试获取每个“艺术家”的收入(来自总“销售额”)，以及他们是否已声明一些销售额，这些数据保存在表“声明”中

这是每个表的结构:

*Table Artist:
Artist_id
Artist_name
Artist_profile

*Table Sales :
Sales_id
Artist_name
Sales_amount

*Tables Claim :
Claim_id
Artist_name
Claim_amount

我尝试了一些查询，但没有得到我预期的结果，某些值在“Claim_amount”列中循环，假设表“sales”有多个数据，表“claim”还没有数据，因为没有 claim 历史记录。

SELECT artist.member_id,artist.profile_pict, sales.artist_name, 
       SUM(sales.amount) AS total_sales ,claim.claim_amount

FROM sales,artist,claim

WHERE sales.artist_name OR claim.artist_name = artist.username

   GROUP BY sales.artist_name
   ORDER BY total_sales DESC 

我希望输出类似于示例:

Artis_id | Artist_profile | Artist_name  | Total_amount | Total_claim
1          Artist A         My Artist 1    100            50
2          Artist B         My Artist 2    200            null (because there is no history)
3          Artist C         My Artist 3    300            150

Answer 1

使用左连接

SELECT a.member_id,a.profile_pict, a.artist_name, 
       SUM(sales.amount) AS total_sales ,sum(claim_amount) as total_claim
FROM artist a left join sales s on a.Artist_name=s.Artist_name
left join claim c on c.Artist_name= a.Artist_name
GROUP BY a.member_id,a.profile_pict, a.artist_name
ORDER BY total_sales DESC 

注意:最好使用显式连接而不是逗号分隔连接