如何获取与分组集中到不同列中的最小值和最大值对应的项目的名称

Question

Table 1 : ORDERS (ORDER_ID, CUSTOMER_ID, ITEM_ID, QUANTITY)

Table 2 : CUSTOMERS (CUSTOMER_ID, CUSTOMER_NAME, ZIPCODE)

Table 3 : ITEMS (ITEM_ID, ITEM_NAME)

Required Output : OUTPUT (ZIPCODE, MAX_ORDERED_ITEM_NAME, MIN_ORDERED_ITEM_NAME

I've tried various approaches to get the output, but haven't been able to get to the end result

Current query:

SELECT ZIPCODE, ITEM_NAME, SUM(QUANTITY) AS SALES
FROM ORDERS
JOIN CUSTOMERS ON ORDERS.CUSTOMER_ID = CUSTOMERS.CUSTOMER_ID
JOIN ITEMS ORDERS.ITEM_ID = ITEMS.ITEM_ID
GROUP BY ZIPCODE, ITEM_NAME
ORDER BY SALES DESC;

Answer 1

You can use analytical function ROW_NUMBER with the group by as following:

 SELECT O.ZIPCODE, MAX(CASE WHEN MAXRN = 1 THEN ITEM_NAME END) AS MAX_ORDERED_ITEM_NAME, MAX(CASE WHEN MINRN = 1 THEN ITEM_NAME END) AS MIN_ORDERED_ITEM_NAME FROM (SELECT O.ZIPCODE, I.ITEM_ID, I.ITEM_NAME, ROW_NUMBER() OVER (PARTITION BY I.ITEM_ID ORDER BY SUM(QUANTITY) ) AS MINRN, ROW_NUMBER() OVER (PARTITION BY I.ITEM_ID ORDER BY SUM(QUANTITY) DESC NULLS LAST) AS MAXRN FROM ORDERS O JOIN ITEMS I ON I.ITEM_ID = O.ITEM_ID JOIN CUSTOMERS C ON C.CUSTOMER_ID = O.CUSTOMER_ID GROUP BY O.ZIPCODE, I.ITEM_ID, I.ITEM_NAME) WHERE 1 IN (MINRN, MAXRN) GROUP BY O.ZIPCODE;

Cheers!!