从每个 GROUP BY (unique_id) 和 ORDER BY 数字中选择具有 MAX id 的行

Question

我有一个包含 id、unique_id 和 order_number 的表。

1. 我想按 unique_id 对行进行分组
2. 我想从每个组中获取具有 MAX id 的行
3. 最后一件事我想按 order_number 对行进行排序

我也有几个 WHERE 子句。这是我的尝试，但不起作用：

SELECT MAX(id) AS id
     , order_number
  FROM table 
 WHERE final = 0 
   AND username = '$username' 
   AND active = 1 
 GROUP 
    BY unique_id 
 ORDER 
     BY order_number

Answer 1

您可以将查询用作子查询：

SELECT *
FROM table 
WHERE id IN (SELECT MAX(id) AS id
             FROM table 
             WHERE final=0 AND username='$username' AND active=1 
             GROUP BY unique_id) 
ORDER BY order_number

或者，如果

id

不唯一，请使用

JOIN

:

SELECT t1.*
FROM table AS t1
JOIN (SELECT MAX(id) AS max_id, unique_id
      FROM table           
      WHERE final=0 AND username='$username' AND active=1 
      GROUP BY unique_id
) AS t2 ON t1.unique_id = t2.unique_id AND t1.id = t2.unique_id
ORDER BY order_number

Answer 2

试试这个：

SELECT id, redni_broj 
FROM table 
WHERE final=0 AND username='$username' AND active=1 AND
    id IN (
              SELECT MAX(id) FROM table table2
              WHERE table.unique_id = table2.unique_id
          )
GROUP BY unique_id 
ORDER BY order_number;

Answer 3

你可以用这个非常简单的方法

SELECT 
    id, MAX(unique_id) as unique_data, order_number
FROM
    table
WHERE final = 0 
AND username = '$username' 
AND active = 1 
GROUP BY unique_data
ORDER BY MAX(unique_data);