Getting COUNT while ignoring GROUP BY - mysql

Question

I have the following table: ProductSales
+-------+-----------+--------+-----------+
|prod_id|customer_id|order_id|supplier_id|
+-------+-----------+--------+-----------+
| 1 | 1 | 1 | 1 |
+-------+-----------+--------+-----------+
| 2 | 4 | 2 | 2 |
+-------+-----------+--------+-----------+
| 3 | 1 | 1 | 1 |
+-------+-----------+--------+-----------+
| 4 | NULL | NULL | Null |
+-------+-----------+--------+-----------+
| 5 | 1 | 1 | 2 |
+-------+-----------+--------+-----------+
| 6 | 4 | 7 | 1 |
+-------+-----------+--------+-----------+
| 7 | 1 | 1 | 3 |
+-------+-----------+--------+-----------+
I have a SELECT query:
SELECT customer_id AS customer, count(*) AS prod_count
, count(DISTINCT order_id) as orders
FROM ProductSales
WHERE supplier_id=1
GROUP BY customer_id
HAVING customer_id<>'NULL'
This will be produce the result:
+--------+----------+------+
|customer|prod_count|orders|
+--------+----------+------+
| 1 | 2 | 1 |
+--------+----------+------+
| 4 | 1 | 1 |
+--------+----------+------+
What I have been trying to achieve and getting nowhere is to add a fourth column in my results to show the number of order_ids that belong only to the current supplier for each customer:
+--------+----------+------+-------------+
|customer|prod_count|orders|Unique Orders|
+--------+----------+------+-------------+
| 1 | 2 | 1 | 0 | } Order '1' is connected with two supplier_ids
+--------+----------+------+-------------+
| 4 | 1 | 1 | 1 | } Order '2' is connected to only one supplier_id
+--------+----------+------+-------------+
(This gets more complex when there are more orders per customer associated with far more suppliers).
I thought I was close with:
SELECT t1.user_id, count(DISTINCT t1.prod_id) AS prod_count
, count(DISTINCT t1.order_id) as orders
, IF(count(DISTINCT t3.supplier_id)>1,0,1) AS Unique_Orders
FROM ProductSales AS t1
LEFT JOIN `order` AS t2 ON t1.order_id=t2.order_id
LEFT JOIN ProductSales AS t3 ON t2.order_id=t3.order_id
WHERE t1.supplier_id=1
GROUP BY t1.customer_id
HAVING t1.customer_id<>'NULL'
The orders table stated above is related to ProductSales only by order_id.
Which shows my Customers, Products(total), Orders(total) but the Unique Orders shows if there are unique orders (0) or not (1), I understand the logic of the IF statement and it does what I expect. It's working out how to find the number of unique orders which is baffling me.
The table is established and can't be changed.
Any suggestions?

Answer 1

Unique orders can be defined as
SELECT OrderID
FROM yourtable
GROUP BY OrderID
Having COUNT(Distinct SupplierID) = 1
So try
SELECT
customer_id AS customer,
count(*) AS prod_count.
count(DISTINCT productsales.order_id) as orders,
COUNT(distinct uqo)
FROM ProductSales
left join
(
SELECT Order_ID uqo
FROM Productsales
GROUP BY Order_ID
Having COUNT(Distinct supplier_id) = 1
) uniqueorders
on ProductSales.order_id = uniqueorders.uqo
WHERE supplier_id=1
GROUP BY customer_id