MySQL的：左加入用戶表數據表返回多行

Question

• 我有2個表：用戶和paypal_transactions
• 對於每個用戶，我們有一個ID（在paypal_transactions表命名USER_ID）
• 用戶可以有幾個paypal_transactions。關係一對多
• 我需要獲取最新的事務ID（由date_dt降序排列），當我做我的查詢

我當前的查詢：

SELECT `Transaction`.*, `User`.*, `Tipster`.`username` 
FROM `pronostics_framework`.`users` AS `User` 
LEFT JOIN `pronostics_framework`.`users` AS `Tipster` ON (`User`.`tipster_id` = `Tipster`.`id`) 
LEFT JOIN `pronostics_framework`.`paypal_transactions` AS `Transaction` ON (`User`.`id` = `Transaction`.`user_id`) 
ORDER BY `User`.`id` DESC 
LIMIT 500 

目前每個用戶一個交易，它工作正常。順便說一句，許多交易，我仍然從paypal_transactions表（最老的，但我想從現在的最新）的第一條。

我做了許多嘗試，沒有成功。

感謝您的幫助！

Answer 1

在這裏你去：

SELECT `Transaction`.*, `User`.*, `Tipster`.`username` 
FROM `pronostics_framework`.`users` AS `User` 
LEFT JOIN `pronostics_framework`.`users` AS `Tipster` ON (`User`.`tipster_id` = `Tipster`.`id`) 
LEFT JOIN (SELECT user_id, MAX(date_dt) AS max_date 
      FROM `pronostics_framework`.paypal_transactions 
      GROUP BY user_id) AS max_trans 
    ON User.id = max_trans.user_id 
LEFT JOIN `pronostics_framework`.`paypal_transactions` AS `Transaction` 
    ON (max_trans.user_id = `Transaction`.`user_id` AND max_trans.max_date = Transation.date_dt) 
ORDER BY `User`.`id` DESC 
LIMIT 500 

另一種方式的基礎上，第一個答案第一個查詢在Retrieving the last record in each group：

SELECT `Transaction`.*, `User`.*, `Tipster`.`username` 
FROM `pronostics_framework`.`users` AS `User` 
LEFT JOIN `pronostics_framework`.`users` AS `Tipster` ON (`User`.`tipster_id` = `Tipster`.`id`) 
LEFT JOIN `pronostics_framework`.`paypal_transactions` AS `Transaction` ON Transaction.user_id = User.id 
LEFT JOIN `pronostics_framework`.paypal_transactions AS Transactions1 
    ON Transactions1.user_id = Transactions.user_id AND Transactions1.user_id > Transactions.user_id 
WHERE Transactions1.user_id IS NULL 
ORDER BY `User`.`id` DESC 
LIMIT 500