Choosing a column that fulfills many conditions in different records

Question

I have got table like this:

+----------+---------+
| Customer | Product |
+----------+---------+
|        1 |       1 |
|        1 |       2 |
|        1 |               


        

Answer 1

You can GROUP BY on the Customer and use conditional aggregation based filtering inside the Having clause. MySQL automatically casts boolean values to 0/1 when using in numeric context.

In order to have a specific Product bought by a Customer, its SUM(Product = ..) should be 1.

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Case 1: Get those customers which have purchased each one of the 1,2,3 products at-least (they may have purchased other products as well).

SELECT Customer
FROM your_table
GROUP BY Customer
HAVING SUM(Product = 1) AND -- 1 should be bought
       SUM(Product = 2) AND -- 2 should be bought
       SUM(Product = 3)     -- 3 should be bought

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If you want exclusivity, i.e., the customer has not bought any other product other than 1,2,3; then you can use the following instead.

Case 2: Get those customers which have purchased only 1,2,3 products and each one of them has been purchased at-least once.

SELECT Customer
FROM your_table
GROUP BY Customer
HAVING SUM(Product = 1) AND  -- 1 should be bought
       SUM(Product = 2) AND  -- 2 should be bought
       SUM(Product = 3) AND  -- 3 should be bought
       NOT SUM(Product NOT IN (1,2,3))  -- anything other 1,2,3 should not be bought