Question

这是学生表：

UID     NAME    SPECIALTY

123456  John    Writing
123456  John    NULL
234567  Jane    Acting
234567  Jane    NULL
345678  Bob     Writing
345678  Bob     NULL

我想运行一个查询，它将删除所有具有重复UID和NULL专业的记录。我正在使用ColdFusion，MSQL 2012。

谢谢。

Answer 1

你能做点什么：

delete
  from students s1
 where specialty is null
   and exists(select 1
                from students s2
               where specialty is not null
                 and s2.uid = s1.uid);

这是Oracle中的相关子查询。不确定你的环境。

Answer 2

在MS-SQL服务器中尝试以下查询，

DELETE FROM
    students 
WHERE
    specialty IS NULL 
    AND UID IN (
        SELECT 
            UID 
        FROM 
            students 
        GROUP BY 
            UID 
        HAVING 
            COUNT(*) > 1
    )

如果其中一个记录具有NULL字段，如何删除重复记录？

2 个答案: