SQL Server 2022

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create table sales 
(
    "customer_id" VARCHAR(1),
    "order_date" DATE,
    "product_id" INTEGER
);

create table menu 
(
    "product_id" INTEGER,
    "product_name" VARCHAR(20),
    "price" INTEGER
);

insert into sales values
(1, '2023-05-10', 1),
(1, '2023-05-11', 2),
(1, '2023-05-12', 3),
(2, '2023-04-10', 1),
(2, '2023-04-11', 2),
(2, '2023-04-12', 3);

insert into menu values
(1, 'Prduct_1', 10),
(2, 'Prduct_2', 20),
(3, 'Prduct_3', 25);
9 rows affected

WITH cte_product AS
(
    SELECT 
        sales.customer_id, menu.product_name, 
        ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date) row_a
    FROM 
        sales
    INNER JOIN 
        menu ON sales.product_id = menu.product_id
)
SELECT *
FROM cte_product
WHERE row_a = 1


customer_id
product_name
row_a


1
Prduct_1
1

2
Prduct_1
1


select customer_id, min(order_date) as min_order_date
from sales s
group by customer_id


customer_id
min_order_date


1
2023-05-10

2
2023-04-10


select s.*
from sales s
inner join (
  select customer_id, min(order_date) as min_order_date
  from sales s
  group by customer_id
) as t on s.customer_id = s.customer_id and s.order_date = t.min_order_date


customer_id
order_date
product_id


1
2023-05-10
1

2
2023-04-10
1


select s.*, m.product_name
from sales s
inner join (
  select customer_id, min(order_date) as min_order_date
  from sales s
  group by customer_id
) as t on s.customer_id = s.customer_id and s.order_date = t.min_order_date
inner join menu m on m.product_id = s.product_id


customer_id
order_date
product_id
product_name


1
2023-05-10
1
Prduct_1

2
2023-04-10
1
Prduct_1