MySQL通过更新/删除整合重复数据记录

我有一张这样的桌子：

mysql> SELECT * FROM Colors;
╔════╦══════════╦════════╦════════╦════════╦════════╦════════╦════════╗
║ ID ║ USERNAME ║  RED   ║ GREEN  ║ YELLOW ║  BLUE  ║ ORANGE ║ PURPLE ║
╠════╬══════════╬════════╬════════╬════════╬════════╬════════╬════════╣
║  1 ║ joe      ║ 1      ║ (null) ║ 1      ║ (null) ║ (null) ║ (null) ║
║  2 ║ joe      ║ 1      ║ (null) ║ (null) ║ (null) ║ 1      ║ (null) ║
║  3 ║ bill     ║ 1      ║ 1      ║ 1      ║ (null) ║ (null) ║ 1      ║
║  4 ║ bill     ║ (null) ║ 1      ║ (null) ║ 1      ║ (null) ║ (null) ║
║  5 ║ bill     ║ (null) ║ 1      ║ (null) ║ (null) ║ (null) ║ (null) ║
║  6 ║ bob      ║ (null) ║ (null) ║ (null) ║ 1      ║ (null) ║ (null) ║
║  7 ║ bob      ║ (null) ║ (null) ║ (null) ║ (null) ║ (null) ║ 1      ║
║  8 ║ bob      ║ 1      ║ (null) ║ (null) ║ (null) ║ (null) ║ (null) ║
╚════╩══════════╩════════╩════════╩════════╩════════╩════════╩════════╝

我想运行一个更新和删除，它将查找和删除重复项，并合并记录，这样我们就可以以此结束

mysql> SELECT * FROM Colors;
╔════╦══════════╦═════╦════════╦════════╦════════╦════════╦════════╗
║ ID ║ USERNAME ║ RED ║ GREEN  ║ YELLOW ║  BLUE  ║ ORANGE ║ PURPLE ║
╠════╬══════════╬═════╬════════╬════════╬════════╬════════╬════════╣
║  1 ║ joe      ║   1 ║ (null) ║ 1      ║ (null) ║ 1      ║ (null) ║
║  3 ║ bill     ║   1 ║ 1      ║ 1      ║ 1      ║ (null) ║ 1      ║
║  6 ║ bob      ║   1 ║ (null) ║ (null) ║ 1      ║ (null) ║ 1      ║
╚════╩══════════╩═════╩════════╩════════╩════════╩════════╩════════╝

---

我知道我可以用一个脚本轻松地完成这项工作，但为了更好地学习和理解MySQL，我想学习如何使用纯SQL完成这项工作。

您真的需要更新基础表吗？如果不是，并且您只需要如示例所示的结果集，您可以简单地对表进行分组：

SELECT   MIN(ID)     AS ID,
         Username    AS Username,
         MAX(Red)    AS Red,
         MAX(Green)  AS Green,
         MAX(Yellow) AS Yellow,
         MAX(Blue)   AS Blue,
         MAX(Orange) AS Orange,
         MAX(Purple) AS Purple
FROM     Colors
GROUP BY Username

---

请在上查看。

这只是一个投影。它不会更新表，也不会删除一些数据

SELECT  MIN(ID) ID,
        Username,
        MAX(Red) max_Red,
        MAX(Green) max_Green,
        MAX(Yellow) max_Yellow,
        MAX(Blue) max_Blue,
        MAX(Orange) max_Orange,
        MAX(Purple) max_Purple
FROM    Colors
GROUP   BY Username

更新

如果确实要删除这些记录，则需要先运行UPDATE语句，然后才能删除这些记录

UPDATE  Colors a
        INNER JOIN
        (
            SELECT  MIN(ID) min_ID,
                    Username,
                    MAX(Red) max_Red,
                    MAX(Green) max_Green ,
                    MAX(Yellow) max_Yellow,
                    MAX(Blue) max_Blue,
                    MAX(Orange) max_Orange,
                    MAX(Purple) max_Purple
            FROM    Colors
            GROUP   BY Username
        ) b ON a.ID = b.Min_ID 
SET     a.Red = b.max_Red,
        a.Green = b.max_Green,
        a.Yellow = b.max_Yellow,
        a.Blue = b.max_Blue,
        a.Orange = b.max_Orange,
        a.Purple = b.max_Purple

然后你现在可以删除这些记录

DELETE  a
FROM    Colors a
        LEFT JOIN
        (
            SELECT  MIN(ID) min_ID,
                    Username
            FROM    Colors
            GROUP   BY Username
        ) b ON a.ID = b.Min_ID 
WHERE   b.Min_ID  IS NULL

---

NULL使这一点更复杂，因为NULL=NULL不是真的，但在SQL中是未知的。如果有0和1，则可以省略颜色条件中或之前的部分。

如果要删除记录，我想您的意思是删除，而不是更新。FrankPI，您是对的。我已将问题更新为包含删除。使用我下面的建议，您不需要中间更新，只需删除一次

DELETE FROM Colors c1
WHERE EXISTS (SELECT 1
                FROM Colors c2
               WHERE c1.Username = c2.Username
                 AND ((c1.Red    IS NULL AND c2.Red    IS NULL) OR c1.Red    = c2.Red   )
                 AND ((c1.Green  IS NULL AND c2.Green  IS NULL) OR c1.Green  = c2.Green )
                 AND ((c1.Yellow IS NULL AND c2.Yellow IS NULL) OR c1.Yellow = c2.Yellow)
                 AND ((c1.Blue   IS NULL AND c2.Blue   IS NULL) OR c1.Blue   = c2.Blue  )
                 AND ((c1.Orange IS NULL AND c2.Orange IS NULL) OR c1.Orange = c2.Orange)
                 AND ((c1.Purple IS NULL AND c2.Purple IS NULL) OR c1.Purple = c2.Purple)
                 AND c2.ID < c1.ID
             )