mysql - 不能只显示多个交易的最大日期

Question

我执行这个查询:

SELECT distinct(accounts.account_id), transactions.trn_code , transactions.trn_date
FROM accounts join transactions ON accounts.account_id = transactions.account_id
WHERE accounts.account_currency = 'USD'  AND accounts.account_cards_linked > 1 
AND transactions.trn_date >= '2015/03/01' AND transactions.trn_date <= '2015/03/31'
GROUP BY transactions.trn_code , transactions.trn_date,accounts.account_id
HAVING transactions.trn_date >= MAX(transactions.trn_date)
ORDER BY accounts.account_id;

我得到了这些结果: click image to see the result grid

我的问题是我希望每个帐户只显示最新日期的交易。但是现在如果一个账户有不止一笔交易，则全部出现。 (例如，我希望账户 912...129 在最近一天 2015/03/05 只出现一次。(示例参见图片)) 有什么想法吗？？

Answer 1

您需要在每个帐户的 MAX(trn_date) 上执行 JOIN:

SELECT
    a.account_id,
    t.trn_code,
    t.trn_date
FROM accounts a
INNER JOIN transactions t
    ON a.account_id = t.account_id
INNER JOIN (
    SELECT
        account_id, MAX(trn_date) AS trn_date
    FROM transactions
    WHERE
        trn_date >= '2015/03/01' 
        AND trn_date <= '2015/03/31'
    GROUP BY account_id
)td
    ON t.account_id = td.account_id
    AND t.trn_date = td.trn_date
WHERE
    a.account_currency = 'USD'
    AND a.account_cards_linked > 1 
ORDER BY a.account_id

注意:使用有意义的表别名来提高可读性和可维护性。