Mysql连接表，但仅包含特定行的结果

Question

three tables: Customers (id_cus, cli_name, ...) Products (id_pro, pro_name, ...) Orders (id_cus, id_pro)

Table Orders is relation between Customers and Products.

Question is: How to get Customers (id_cus) who choose only specific product.

Example: Product A (id_pro= 100) and want all Clients customers who only bought this Product A , not Product A and Product B . Only Product A (id_pro = 100).

SELECT `id_cus` from `Orders` where `id_pro=100;

This give me all Customers who have ever bought Product A (and maybe Product B, C too).

Sorry, no idea.

Answer 1

Take a look to EXISTS

Simply:

SELECT o.id_cus
FROM orders o
WHERE o.id_pro = 100
    AND NOT EXISTS (SELECT * from orders o2 where o2.id_cus = o.id_cus AND o2.id_pro != 100)

Answer 2

You can use aggregation for this:

select o.id_cus
from orders o
group by o.id_cus
having min(o.id_pro) = max(o.id_pro) and min(o.id_pro) = 100;