查找列缺号

Question

我在T-SQL此列：

1 
2 
3 
7 
10 

有SQL中为序列4,5,6和8,9 我有尝试检测丢失号码的功能 类似 如果（ab> 1）那么我们有一个缺少的号码

与coalesce但我不明白。 感谢任何方向

Answer 1

你可以试试这个：

DELCARE @a 
SET @a = SELECT MIN(number) FROM table 
WHILE (SELECT MAX(number) FROM table) > @a 
BEGIN 
IF @a NOT IN (SELECT number FROM table) 
PRINT @a 
SET @a=@a+1 
END 

Answer 2

下面的查询将找出每个序列开始和数量缺失：

select t.col + 1 as MissingStart, (nextval - col - 1) as MissingSequenceLength 
from (select t.col, 
      (select min(t.col) from t t2 where t2.col > t.col) as nextval 
     from t 
    ) t 
where nextval - col > 1 

这是通过使用相关子查询获取表格中的下一个值。

Answer 3

我知道这是一个迟到的回答，但这里是一个使用递归表表达式得到一个表中的最小值和最大值之间的遗漏值的查询：

WITH CTE AS 
(
    --This is called once to get the minimum and maximum values 
    SELECT nMin = MIN(t.ID), MAX(t.ID) as 'nMax' 
    FROM Test t 
    UNION ALL 
    --This is called multiple times until the condition is met 
    SELECT nMin + 1, nMax 
    FROM CTE 
    WHERE nMin < nMax 
) 

--Retrieves all the missing values in the table. 
SELECT c.nMin 
FROM CTE c 
WHERE NOT EXISTS 
(
    SELECT ID 
    FROM Test 
    WHERE c.nMin = ID 
) 

这是用下面的测试模式：

CREATE TABLE Test 
(
    ID int NOT NULL 
) 

INSERT INTO Test 
    Values(1) 

INSERT INTO Test 
    Values(2) 

INSERT INTO Test 
    Values(3) 

INSERT INTO Test 
    Values(7) 

INSERT INTO Test 
    Values(10)