Question

我有两张桌子

用户：id，name

health：id，status，test_date，user_id

包含用户健康历史记录的健康状况表

现在我想获得特定用户的最后一次健康测试和用户信息

我试过了这个查询

SELECT users.*, health.* FROM users INNER JOIN health ON users.id=health.user_id
having (max(health.id)) order by users.id desc limit 50

但我失败了

Answer 1

试试这个：

SELECT users.*, health.* FROM users  
INNER JOIN health  
    ON health.id = (SELECT id FROM health WHERE health.id = users.id ORDER BY id DESC LIMIT 1)

Answer 2

这是另一个选择：

SELECT U.*, H.* 
FROM users AS U
  INNER JOIN (
    SELECT user_id, MAX(id) AS id
    FROM health
    GROUP BY user_id
  ) AS D
    ON D.user_id = U.user_id
  INNER JOIN health AS H
    ON H.id = D.id

注意：“ D” 将导致DERIVED表，因此在MySQL 5.7+或MariaDB 10+中执行速度更快。

参考：

获得一对多关系的最后记录

2 个答案: