Question

如果我有一个包含两列的表，名称和时间戳，以及一堆将具有共享名称的行。如何选择共享同一名称的每组行的最新行？

谢谢！

Answer 1

SELECT name, MAX(timestamp) FROM Table1 GROUP BY name

编辑：根据评论，请尝试以下方法：

SELECT name, timestamp, col3, col4
FROM   Table1 t1
WHERE  timestamp = (SELECT MAX(t2.timestamp)
              FROM Table1 t2
              WHERE t1.name = t2.name);

由Mchl

添加

没有依赖子查询的版本（应该表现更好）

SELECT 
  t1.name, t1.timestamp, t1.col3, t1.col4
FROM   
  Table1 AS t1
CROSS JOIN (
  SELECT 
    name, MAX(timestamp) AS timestamp
  FROM 
    Table1
  GROUP BY
     name
) AS sq
USING (name,timestamp)

Answer 2

然后你需要一个子查询：

SELECT columns 
FROM Table1 t1
WHERE row_id = (SELECT row_id 
                FROM table1 t2
                WHERE t1.name = t2.name
                ORDER BY timestamp DESC 
                LIMIT 1)
GROUP BY name

已编辑，已忘记按名称分组

简单的MYSQL明显选择

2 个答案: