返回 group by SQL 中 min 和 max 函數對應的分類值

Question

我有一個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

我嘗試了以下

此查詢應作為分組工作，從第一個條目中選取分類值

-)select USER_ID, Min(TRANSACTION_DATE),MERCHANT_NAME from transactions
Group by USER_ID

Answer 1

使用ROW_NUMBER我們可以嘗試：

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;