Sql server MS SQL 2012：查找数字序列

我有一张这样的桌子：

    WITH S AS (
    SELECT 'B' type, 1 number
UNION SELECT 'B', 2
UNION SELECT 'B', 3
UNION SELECT 'B', 4
UNION SELECT 'B', 5
UNION SELECT 'A', 6
UNION SELECT 'A', 7
UNION SELECT 'B', 8
UNION SELECT 'B', 9
UNION SELECT 'B', 10
UNION SELECT 'C', 11
UNION SELECT 'A', 12
UNION SELECT 'B', 13
UNION SELECT 'B', 14
UNION SELECT 'B', 15
UNION SELECT 'B', 16
UNION SELECT 'B', 17
UNION SELECT 'A', 18
UNION SELECT 'C', 19
UNION SELECT 'B', 20
UNION SELECT 'B', 21
    ) 

如何获得每种类型的一行（例如，3个或更多）不同的数字序列？ 例如，对于B1~5，会有类似“B1”的东西，对于B8~10，会有类似“B2”的东西。我怀疑应该有类似于

LEAD/LAG

和

densite_-RANK（）

的组合，但不知道如何应用。数字是唯一的，如果这很重要的话

结果应该如下所示：

Type   Number  Sequence
-----------------------
B        1        B1
B        2        B1
B        3        B1
B        4        B1
B        5        B1
A        6        NULL
......................
B        8        B2
B        9        B2
B        10       B2
C        11       NULL
A        12       NULL
B        13       B3
....................
B        17       B3

---

一种方法是结合使用和的差异

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有一个回复，仅几分钟，它包含了我想要的确切解决方案（其余我可以想出）：

无法对答案进行评分-该答案已被删除。

---

解决办法是找到“差距和岛屿”——现在我知道了。

我不明白你在这里想做什么。你能解释一下要求吗？

WITH S AS (
    SELECT 'B' type, 1 number
UNION SELECT 'B', 2
UNION SELECT 'B', 3
UNION SELECT 'B', 4
UNION SELECT 'B', 5
UNION SELECT 'A', 6
UNION SELECT 'A', 7
UNION SELECT 'B', 8
UNION SELECT 'B', 9
UNION SELECT 'B', 10
UNION SELECT 'C', 11
UNION SELECT 'A', 12
UNION SELECT 'B', 13
UNION SELECT 'B', 14
UNION SELECT 'B', 15
UNION SELECT 'B', 16
UNION SELECT 'B', 17
UNION SELECT 'A', 18
UNION SELECT 'C', 19
UNION SELECT 'B', 20
UNION SELECT 'B', 21
    ) 
SELECT type, 
       number, 
       sequence = CASE 
            WHEN type = 'B' 
            THEN 'B' + CAST(DENSE_RANK() OVER (ORDER BY CASE WHEN type = 'B' THEN 0 ELSE 1 END, RN) AS VARCHAR(10)) 
            END
FROM (
    SELECT *, RN = ROW_NUMBER() OVER (ORDER BY number) - ROW_NUMBER() OVER (PARTITION BY type ORDER BY number)
    FROM S
    ) AS T
ORDER BY number;

SELECT type, R1 = min(number), R2 = max(number) FROM (
SELECT *, number - ROW_NUMBER() OVER (PARTITION BY type ORDER BY number) Grp From S
) A
GROUP BY type