Question

我有以下代码

SELECT 
    PhysicalAddressID
FROM 
    tblPhysicalAddresses  as a
WHERE EXISTS 
(
    SELECT 
        PhysicalAddressID
    FROM 
        tblPhysicalAddresses as b
    WHERE
        a.PhysicalAddressID <> b.PhysicalAddressID AND

        a.Address1 = b.Address1 AND
        a.Address2 = b.Address2 AND
        a.Address3 = b.Address3 AND
        a.City = b.City AND
        a.CountryID = b.CountryID AND
        a.PersonID = b.PersonID AND
        a.PhysicalAddressTypeID = b.PhysicalAddressTypeID AND
        a.PostalCode = b.PostalCode AnD
        a.Province = b.Province AND
        a.StateID = b.StateID AND
        a.ZipCode = b.ZipCode

)

我可以直观地查看数据并查看是否存在匹配项。但是，当我运行查询时，它什么都不返回。这可能是由于可空列的比较？如果是这样，那么替代方案。目标是找到重复的行。

例如，列的列为null的实例。找不到匹配项，尽管它们都是空的。

基本上我有80个具有相同模式的数据库。我决定将它们合并为一个。但是有重复的地址。因此，我的目标是合并重复的地址。

Answer 1

您可以使用this technique将两个对应的空值评估为相等

WHERE
    a.PhysicalAddressID <> b.PhysicalAddressID
          AND EXISTS (SELECT a.Address1, a.Address2 
                      INTERSECT
                      SELECT b.Address1, b.Address2)

（剩下的栏目留给你填写）

Answer 2

我建议将其作为聚合：

SELECT a.Address1, a.Address2, a.Address3, a.City, a.CountryID, a.PersonID,
       a.PhysicalAddressTypeID, a.PostalCode, a.Province, a.StateID, a.ZipCode,
       COUNT(*) as NumPhysicalAddresses,
       MIN(a.PhysicalAddressId), MAX(a.PhysicalAddressId)
FROM tblPhysicalAddresses a
GROUP BY a.Address1, a.Address2, a.Address3, a.City, a.CountryID, a.PersonID,
         a.PhysicalAddressTypeID, a.PostalCode, a.Province, a.StateID, a.ZipCode
HAVING COUNT(*) > 1;

在找不到比赛时你可能面临许多问题：

其中一个或多个列为NULL（group by版本将会捕获）。
字符串中的空格和/或其他不可见字符。
类似字符，例如大写字母O和数字0。
虽然许多字段可能重叠，但缺少完全重复的内容。

Answer 3

不清楚你想要什么，但这可能是它

SELECT a.PhysicalAddressID 
  FROM tblPhysicalAddresses as b
  JOIN tblPhysicalAddresses as b
    ON a.PhysicalAddressID <> b.PhysicalAddressID 
   AND (a.Address1 = b.Address1 or (a.Address1 is null and b.Address1 is null))
   AND (a.Address2 = b.Address2 or (a.Address2 is null and a.Address2 is null)) 
   AND (a.Address3 = b.Address3 or (a.Address2 is null and b.Address3 is null)) 
   AND  ...

将列与Null进行比较

3 个答案: