[英]How to find gaps in a sequence of numbers in SQL Server
I am trying to find the smallest missing number in this table. 我正尝试在此表中找到最小的遗漏号码。
+------+--------+
| id | number |
+------+--------+
| 902 | 1 |
| 908 | 2 |
| 1007 | 7 |
| 1189 | 8 |
| 1233 | 12 |
| 1757 | 15 |
+------+--------+
In the number column, you can see there are several gaps between the numbers. 在数字列中,您可以看到数字之间存在多个间隙。 I need to get the number after the smallest gap.
我需要在最小间距后得到数字。 So in the case above I need the number 3. Because 2 is the smallest number after a gap.
因此,在上述情况下,我需要数字3。因为2是间隔后的最小数字。
I would use lead()
: 我会用
lead()
:
select min(id) + 1
from (select t.*,
lead(id) over (order by id) as next_id
from t
) t
where next_id <> id + 1;
If you want to ensure that the ids start at 1 (so if "1" is missing, then return that), you can do: 如果要确保ID从1开始(因此,如果缺少“ 1”,则返回该ID),可以执行以下操作:
select (case when min(minid) <> 1 then 1 else min(id) + 1 end)
from (select t.*, min(id) over () as minid
lead(id) over (order by id) as next_id
from t
) t
where next_id <> id + 1;
Lots of different ways here is one that is probably popular these days due to using window functions. 由于使用窗口函数,许多方式在当今可能很流行。
;WITH cte AS (
SELECT
Id
,[Number]
,LAG([Number],1,NULL) OVER (ORDER BY [Number] ASC) AS LagValue
FROM
@Table
)
SELECT
MIN(LagValue) + 1 AS SmallestNumberAfterGap
FROM
cte
WHERE
LagValue <> [Number] - 1
And here is one that is less overall code using an LEFT JOIN
这是使用
LEFT JOIN
减少整体代码的一种
SELECT
MIN(t2.[Number]) + 1 AS SmallestNumberAfterGap
FROM
@Table t1
LEFT JOIN @Table t2
ON t1.Number + 1 = t2.Number
And because I am just writing more code here is one using EXISTS
因为我只是在写更多代码,所以这里是使用
EXISTS
代码
SELECT
MIN(t1.Number) + 1 AS SmallestNumberAfterGap
FROM
@Table t1
WHERE
NOT EXISTS (SELECT * FROM @Table t2 WHERE t1.Number + 1 = t2.Number)
Here is a link showing all 3 options functioning http://rextester.com/TIFRI87282 这是一个链接,显示所有3个起作用的选项http://rextester.com/TIFRI87282
This solution will give you the minimum numbers missing from sequence not a single number .. This uses a numbers table .. 此解决方案将为您提供序列中缺少的最小数字,而不是单个数字..这将使用数字表 。
;With cte
as
(
select
*
from
Numbers n
left join
#t1
on n.Number=#t1.num
where n.Number<=(select max(num) from #t1)
)
select
number from cte c1
join
#t1
on #t1.num+1=c1.Number
where c1.num is null
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.