Question

是否有可能只使用列（日期）排序的其他表中的一行进行LEFT JOIN而不使用子查询。我的查询如下。它有效，但速度超慢。

SELECT * FROM clients c 
LEFT JOIN loan l ON c.id = l.id_client AND l.id = (
    SELECT id FROM loan ll
    WHERE ll.id_client = c.id
    ORDER BY `create_date` DESC
    LIMIT 1) 
GROUP BY k.id DESC 
ORDER BY c.register_date DESC 
LIMIT n , m; (n,m is from pagination)

有没有办法加快速度？

Answer 1

我将您的问题解释为“获取每位客户最近贷款的所有贷款详情”

这应该有用......但要注意这个假设。

SELECT * 
FROM 
    clients c 
    LEFT JOIN (select id_client, Max(id) id -- this assumes that a loan with a later create date will also have a higher id.
                from loan
                group by id_client) il
        on il.id_client = c.id
    inner join loan l
        on l.id = il.id
GROUP BY k.id DESC                          -- Dont know what "k" is
ORDER BY c.register_date DESC 
LIMIT n , m; (n,m is from pagination)

MySQL LEFT JOIN只有一行，按列排序，没有子查询

1 个答案: