提取Postgres中最小日期的金额

Question

非常基本：我有一个表格，其中包含日期，帐户和该日期特定帐户所完成的金额。我遇到了一个非常基本的问题-获取每个帐户的最短日期金额。

输入：

所需：

如果我在下面的查询中进行查询，显然也会返回按金额分组。

SELECT account_ref         AS account_alias, 
       Min(timestamp_made) AS reg_date, 
       amount 
FROM   stg_payment_mysql 
GROUP  BY account_ref, 
          amount 

Answer 1

也许最有效的方法是使用DISTINCT ON：

SELECT DISTINCT ON (account) account, date, amount
FROM stg_payment_mysql
ORDER BY account, date;

更通用的ANSI SQL方法将使用ROW_NUMBER：

WITH cte AS (
    SELECT account, date, amount,
        ROW_NUMBER() OVER (PARTITION BY account ORDER BY date) rn
    FROM stg_payment_mysql
)

SELECT account, date, amount
FROM cte
WHERE rn = 1
ORDER BY account;