Question

我试图通过在两列下找到重复项来删除表中的记录。

我已设法使用以下内容识别记录;

SELECT SiteName, Postcode 
FROM [Active Site Locations]
GROUP BY SiteName, Postcode
HAVING count(*) > 1;

但是，当我尝试运行DELETE将其从表中删除时，我得到以下内容。

DELETE FROM [Active Site Locations] 
WHERE (Select SiteName, Postcode, count(*) FROM [Active Site Locations]
GROUP BY SiteName, Postcode
HAVING count(*) >1 );

您有一个子查询可以返回多个字段而不使用主查询的from子句中的EXISTS保留字。修改子查询的select语句以仅请求一个字段。

但我需要检查SiteName和Postcode列，如果匹配，那么我需要删除它们，请有人帮忙。

Answer 1

这是一个方法，它使用相关子查询来计算匹配数，然后在外部查询中使用> 1进行比较：

DELETE FROM [Active Site Locations]
WHERE (SELECT COUNT(*)
       FROM [Active Site Locations] as asl          
       WHERE asl.SiteName = [Active Site Locations].SIteName AND
             asl.Postcode = [Active Site Locations].Postcode
      ) > 1;

使用多个列从表中删除重复项

1 个答案: