在访问表中查找缺失的序列号

Question

我在 Access 2003 数据库中有一个 MS Access 表，名为 Comments，在 Comments 表中有一个名为 Sequence Number 的列。 序列号列的数字范围从 1 到 20000。但是，序列号列中缺少某些数字，我希望能够查看丢失的数字，例如在下面我想运行访问查询以查看4 不见了。

Sequence Number
 1
 2
 3
 5
 6

我在 SQL 视图中使用以下 Access 查询来获取我想要的内容。

SELECT ([Sequence Number]+1) AS MissingFrom, DMin("Sequence Number","Comments","Sequence Number>" & [Sequence Number]) AS MissingUntil
FROM Comments
WHERE (((DMin("Sequence Number","Comments","Sequence Number>" & [Sequence Number]))<>([Sequence Number]+1)));

但是，当我运行查询时，出现以下错误：

Syntax error (missing operator) in query expression 'Min(Sequence Number)'. 

有人可以指出导致查询失败的原因吗？ 谢谢！

Answer 1

NOT EXISTS ：

SELECT MIN([Sequence Number]) + 1 
FROM Comments AS c
WHERE
  c.[Sequence Number] < (SELECT MAX([Sequence Number]) FROM Comments)
  AND NOT EXISTS (
    SELECT 1 FROM Comments
    WHERE [Sequence Number] = c.[Sequence Number] + 1
  )

Answer 2

您可以使用以下方法获得缺失系列中的第一个：

select num + 1
from comments
where num + 1 not in (select num from comments) and
      num + 1 <> (select max(num) from comments);