Get Min value and another column value from the same row

Question

hi all - for each customer and product, I need to grab the row that has the min value for field Value1. I could've just done group by on customer and product and min on Value1, but I also need to grab Vlaue2 from the same row where the minimum value for
Value1 lies.
DECLARE @Temp TABLE (CustomerID INT, ProductID VARCHAR(10), Trans_Date Date, Value1 INT, Value2 INT)
INSERT INTO @Temp VALUES (123, 'ABC', '1/1/2013', 10, 100)
INSERT INTO @Temp VALUES (456, 'ASD', '1/1/2013', 40, 500)
INSERT INTO @Temp VALUES (456, 'ASD', '2/1/2013', 90, 700)
INSERT INTO @Temp VALUES (123, 'ABC', '2/1/2013', 20, 700)
SELECT * FROM @Temp
The output should be
123, ABC, 10, 100
456, ASD, 40, 500
I know that I can just join the table to itself and get the desired output but I am dealing with a table that has millions of rows and I was hoping there is more efficient way to do this. any help would be highly appreciated...

Answer 1

Here is a correction on your DDL to make it into nearly valid table.
CREATE TABLE Sales
(customer_id INTEGER NOT NULL,
product_id CHAR(10) NOT NULL,
transaction_date DATE NOT NULL,
PRIMARY KEY (customer_id, product_id, transaction_date),
value1 INTEGER NOT NULL,
value2 INTEGER NOT NULL);
Here is the current syntax for insertion:
INSERT INTO Sales
VALUES (123, 'abc', '2013-01-01', 10, 100),
(456, 'asd', '2013-01-01', 40, 500),
(456, 'asd', '2013-02-01', 90, 700),
(123, 'abc', '2013-02-01', 20, 700);
WITH
X
AS
(SELECT customer_id, product_id, transaction_date, value1, value2,
MIN(value1) OVER () AS value1_min
FROM Sales)
SELECT X.*
FROM X
WHERE X.value1_min = X.value1;
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