Question

背景：我的雇主有一个由真正旧版本的MySQL（3.23）驱动的数据库。我被要求在数据库中找到重复的序列号和MAC地址。

我能够找到重复的序列号，但由于这个版本的MySQL不支持子查询，我不得不求助于使用临时表。这些是我最终使用的两个SQL语句：

CREATE TEMPORARY TABLE IF NOT EXISTS Inventory_Duplicate_Serials
SELECT Serial
FROM Inventory
WHERE Serial IS NOT NULL
GROUP BY Serial
HAVING COUNT(Serial) > 1

SELECT DeviceName, Model, Inventory.Serial
FROM Inventory
INNER JOIN Inventory_Duplicate_Serials
ON Inventory.Serial = Inventory_Duplicate_Serials.Serial
ORDER BY Serial

现在我需要找到重复的MAC地址。问题是“库存”表有三个MAC地址字段（MAC，MAC2和MAC3）。因此，例如，如果项目的“MAC”字段的值与另一个项目的“MAC2”字段的值相同，我需要知道它。我该怎么做呢？谢谢你的时间。

更新：已解决。我最终创建了两个临时表（Inventory_All_MACs和Inventory_Duplicate_MACs）。这是五个查询：

CREATE TEMPORARY TABLE IF NOT EXISTS Inventory_All_MACs
SELECT MAC
FROM Inventory
WHERE MAC != ''

CREATE TEMPORARY TABLE IF NOT EXISTS Inventory_All_MACs
SELECT MAC2 AS MAC
FROM Inventory
WHERE MAC2 != ''

CREATE TEMPORARY TABLE IF NOT EXISTS Inventory_All_MACs
SELECT MAC3 AS MAC
FROM Inventory
WHERE MAC3 != ''

CREATE TEMPORARY TABLE IF NOT EXISTS Inventory_Duplicate_MACs
SELECT MAC
FROM Inventory_All_MACs
GROUP BY MAC
HAVING COUNT(MAC) > 1

SELECT DeviceName, Model, Inventory_Duplicate_MACs.MAC AS DuplicateMAC, Inventory.MAC, MAC2, MAC3
FROM Inventory_Duplicate_MACs
INNER JOIN Inventory
ON Inventory.MAC  = Inventory_Duplicate_MACs.MAC
OR Inventory.MAC2 = Inventory_Duplicate_MACs.MAC
OR Inventory.MAC3 = Inventory_Duplicate_MACs.MAC
ORDER BY Inventory_Duplicate_MACs.MAC, DeviceName, Model

谢谢大家！

Answer 1

想到一个“简单”的解决方案是创建第二个临时表，列出一列中的所有MAC地址，因此您需要为第一个临时表中的一个条目创建三个条目。

Answer 2

对这个答案不是100％肯定，但使用LEFT JOINS可能值得尝试，例如：

SELECT address1
FROM addresses
LEFT JOIN Inventory_Duplicate_Addresses ad1
ON Addresses.MAC = ad1.mac
LEFT JOIN Inventory_Duplicate_Addresses ad2
ON Addresses.MAC = ad2.mac2
LEFT JOIN Inventory_Duplicate_Addresses ad3
ON Addresses.MAC = ad3.mac3

Answer 3

CREATE TEMPORARY TABLE IF NOT EXISTS Inventory_Mac
  SELECT Mac
  FROM Inventory

INSERT INTO Inventory_Mac
  SELECT Mac2
  FROM Inventory

INSERT INTO Inventory_Mac
  SELECT Mac3
  FROM Inventory

CREATE TEMPORARY TABLE IF NOT EXISTS Inventory_Duplicate_Mac
  SELECT Mac, COUNT(*) AS cnt
  FROM Inventory_Mac
  GROUP BY Mac
  HAVING COUNT(*) > 1


SELECT DeviceName, Model, im.Mac, i.Mac, i.Mac2, i.Mac3
FROM Inventory_Duplicate_Mac AS im
  JOIN Inventory AS i
    ON    i.Mac  = im.Mac
       OR i.Mac2 = im.Mac
       OR i.Mac3 = im.Mac
ORDER BY im.Mac

MySQL：在多个字段中查找重复项

3 个答案: