我的原始数据如下:
sid id amount 1 12 30 2 45 30 3 45 50 4 78 80 5 78 70
所需的输出如下:
sid id amount 1 12 30 2 45 30 3 45 30 4 78 80 5 78 80
目的是获取 id 第一次出现的金额并在第二次出现时更新该金额 我正在尝试以下代码:
UPDATE foo AS f1 JOIN ( SELECT cur.sl, cur.id, cur.amount AS balance FROM foo AS cur JOIN foo AS prev ON prev.id = cur.id GROUP BY cur.tstamp ) AS p ON p.id = a.id SET a.amount = p.amount ;
P粉9044509592024-01-29 20:23:49
将表连接到一个查询,该查询返回每个 id
的最小值 sid
并再次返回其自身,以便获得具有该最小值 sid
的行:
UPDATE tablename t1 INNER JOIN ( SELECT MIN(sid) sid, id FROM tablename GROUP BY id ) t2 ON t2.id = t1.id AND t2.sid < t1.sid INNER JOIN tablename t3 ON t3.sid = t2.sid SET t1.amount = t3.amount;
查看演示。
对于 MySql 8.0+,如果使用 ROW_NUMBER()
窗口函数,则只需 1 个连接即可完成:
UPDATE tablename t1 INNER JOIN ( SELECT *, ROW_NUMBER() OVER (PARTITION BY id ORDER BY sid) rn FROM tablename ) t2 ON t2.id = t1.id SET t1.amount = t2.amount WHERE t2.rn = 1;
查看演示。