mysql - 更新同一张表上的百分比计算

Question

我有一张这样的桌子：

ItemID      PersonID  Score      Percentage
==========================================
1             1       10         [ = 10 / 10+30 = 25%]
1             2       30         [ = 30 / 10+30 = 75%]
2             1       20         [ = 20 / 20+40 = 33%]
2             2       40         [ = 40 / 20+40 = 67%]

“百分比”上的数据不输入，而是按一定的时间间隔自动计算。计算方法是百分比 = 分数 / ItemID 的总分数

我没有使用“SELECT-do the maths-UPDATE”方法，而是尝试编写一个 SQL 来更新“百分比”。

我尝试的是这样的：

UPDATE tb_temp AS t1 
    SET t1.Percentage = 
        CEIL( t1.Score / 
            (SELECT SUM(t2.Score) FROM tb_temp AS t2 WHERE t2.ItemID = t1.ItemID)
        );

但它不起作用。（错误代码：1093 您不能在 FROM 子句中指定目标表 't1' 进行更新）。

任何想法？

Answer 1

UPDATE tb_temp AS t1 
    SET t1.Percentage = 
        CEIL( t1.Score / 
            (SELECT SUM(t2.Score) FROM tb_temp AS t2 left join tb_temp AS t3 on t2.ItemID = t3.ItemID)
        );

Answer 2

尝试：

  UPDATE tb_temp t1 
     JOIN (SELECT ItemId, SUM(t2.Score) TotalScore
           FROM tb_temp 
           group by ItemId) t2 ON t2.ItemID = t1.ItemID
  SET t1.Percentage = CEIL( t1.Score / t2.TotalScore)