MySQL INNER JOIN 从第二个表中只选择一行

沃梦达教程数据库问题

2021-01-01

MySQL INNER JOIN select only one row from second table(MySQL INNER JOIN 从第二个表中只选择一行)

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问题描述

我有一个 users 表和一个 payments 表，对于每个有付款的用户，在 payments表.我想选择所有有付款的用户，但只选择他们最近的付款.我正在尝试这个 SQL，但我以前从未尝试过嵌套 SQL 语句，所以我想知道我做错了什么.感谢帮助


I have a users table and a payments table, for each user, those of which have payments, may have multiple associated payments in the payments table. I would like to select all users who have payments, but only select their latest payment. I'm trying this SQL but i've never tried nested SQL statements before so I want to know what i'm doing wrong. Appreciate the help
SELECT u.* 
FROM users AS u
    INNER JOIN (
        SELECT p.*
        FROM payments AS p
        ORDER BY date DESC
        LIMIT 1
    )
    ON p.user_id = u.id
WHERE u.package = 1


推荐答案
您需要有一个子查询来获取每个用户 ID 的最新日期.
You need to have a subquery to get their latest date per user ID.
SELECT  a.*, c.*
FROM users a 
    INNER JOIN payments c
        ON a.id = c.user_ID
    INNER JOIN
    (
        SELECT user_ID, MAX(date) maxDate
        FROM payments
        GROUP BY user_ID
    ) b ON c.user_ID = b.user_ID AND
            c.date = b.maxDate
WHERE a.package = 1


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