Question

I have these tables:

customer -------- customer_id int name        varchar(255)  order ----- order_id    int customer_id int discount    boolean 

I can get the number of orders made by each customer with a query like:

select c.id, count(o.order_id) from customer c  left join order as o using c.customer_id = o.customer_id group by 1 

Alternatively, I can get the number of discounted orders made by each customer with:

select c.id, count(o.order_id) from customer c  left join order as o using c.customer_id = o.customer_id and o.discount = true group by 1 

But I can’t figure out a way to get both in a single query. I’ve tried the following:

select c.id, count(o.order_id), count(o2.order_id) from customer c  left join order as o using c.customer_id = o.customer_id left join order as o2 using c.customer_id = o2.customer_id and o2.discount = true group by 1 

But it didn’t work. Is it possible to calculate both in a single (MySql) query?

Cheers, Don

Answer 1

How about something like

select c.id, count(o.order_id),sum(if(o.discount,1,0)) from customer c  left join order as o using c.customer_id = o.customer_id group by c.id