[英]Return the corresponding categorical values for min and max functions in group by SQL
I have a transaction table with the following columns: TRANSACTION_ID,USER_ID,MERCHANT_NAME,TRANSACTION_DATE,AMOUNT我有一个包含以下列的交易表:TRANSACTION_ID,USER_ID,MERCHANT_NAME,TRANSACTION_DATE,AMOUNT
-1) query to find the first merchant a user transacts on
-2) query to find the last merchant a user transacts on
I tried the following我尝试了以下
This query should work as group by picks up categorical value from the 1st entry此查询应作为分组工作,从第一个条目中选取分类值
-)select USER_ID, Min(TRANSACTION_DATE),MERCHANT_NAME from transactions
Group by USER_ID
Using ROW_NUMBER
we can try:使用
ROW_NUMBER
我们可以尝试:
WITH cte AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY USER_ID ORDER BY TRANSACTION_DATE) rn1,
ROW_NUMBER() OVER (PARTITION BY USER_ID ORDER BY TRANSACTION_DATE DESC) rn2
FROM transactions
)
SELECT USER_ID,
MAX(CASE WHEN rn1 = 1 THEN MERCHANT_NAME END) AS FIRST_MERCHANT_NAME,
MAX(CASE WHEN rn2 = 1 THEN MERCHANT_NAME END) AS LAST_MERCHANT_NAME
FROM cte
GROUP BY USER_ID;
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