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Supercloud Customer [Microsoft SQL Interview Question]
A Microsoft Azure Supercloud customer is defined as a company that purchases at least one product from each product category.
Write a query that effectively identifies the company ID of such Supercloud customers.
As of 5 Dec 2022, data in the and tables were updated.
Table:
| Column Name | Type |
|---|---|
| customer_id | integer |
| product_id | integer |
| amount | integer |
Example Input:
| customer_id | product_id | amount |
|---|---|---|
| 1 | 1 | 1000 |
| 1 | 3 | 2000 |
| 1 | 5 | 1500 |
| 2 | 2 | 3000 |
| 2 | 6 | 2000 |
Table:
| Column Name | Type |
|---|---|
| product_id | integer |
| product_category | string |
| product_name | string |
Example Input:
| product_id | product_category | product_name |
|---|---|---|
| 1 | Analytics | Azure Databricks |
| 2 | Analytics | Azure Stream Analytics |
| 4 | Containers | Azure Kubernetes Service |
| 5 | Containers | Azure Service Fabric |
| 6 | Compute | Virtual Machines |
| 7 | Compute | Azure Functions |
Example Output:
| customer_id |
|---|
| 1 |
Explanation:
Customer 1 bought from Analytics, Containers, and Compute categories of Azure, and thus is a Supercloud customer. Customer 2 isn't a Supercloud customer, since they don't buy any container services from Azure.
The dataset you are querying against may have different input & output - this is just an example!
Solution
As usual, take a step back and identify the key points of solving the task. This is how we see it:
- In addition to the contracts data, we also need the product category information, thus we need to join the tables.
- Identify the customers with purchases from all of the product categories (i.e. Supercloud customers).
- Output the Supercloud customer IDs.
Step 1
Join the two tables with either or .
Step 2
Now, let's count all of the distinct product categories that a customer has purchased a product from.
| customer_id | unique_count |
|---|---|
| 1 | 3 |
| 7 | 3 |
Step 3
We are almost there, hang on!
Let's wrap the previous step into a CTE, and select only the users who have products from all of the categories.
One way of doing this would be simply filtering for of 3 (as there are 3 product categories). However, let's be even smarter and make it dynamic by using a subquery referencing the products table instead.
I believe this is a pretty nice solution, don't you?
PostgreSQL 14