查找列缺號

Question

我在T-SQL此列：

1 
2 
3 
7 
10 

有SQL中爲序列4,5,6和8,9 我有嘗試檢測丟失號碼的功能 類似 如果（ab> 1）那麼我們有一個缺少的號碼

與coalesce但我不明白。 感謝任何方向

Answer 1

你可以試試這個：

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

下面的查詢將找出每個序列開始和數量缺失：

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 

這是通過使用相關子查詢獲取表格中的下一個值。

Answer 3

我知道這是一個遲到的回答，但這裏是一個使用遞歸表表達式得到一個表中的最小值和最大值之間的遺漏值的查詢：

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 
) 

這是用下面的測試模式：

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)