Tsql 在t-sql中生成具有可变长度的给定字符集的所有可能排列

我编写了下面的脚本来生成指定字符集的所有可能排列

在允许在运行时指定长度的同时，有没有一种方法可以有效地做到这一点

DECLARE @string NVARCHAR(MAX)
SELECT @string = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';

DECLARE @Chars TABLE (
    C CHAR(1) PRIMARY KEY
)

DECLARE @N INT 
SET @N = 1 
WHILE @N <= LEN(@string) BEGIN
    INSERT @Chars (
        C
    ) VALUES (
        SUBSTRING(@string, @N, 1)
    )

    SET @N = @N + 1
END

--SELECT * FROM @Chars


SELECT
    A.C + B.C + C.C
FROM @Chars A, @Chars B, @Chars C
ORDER BY
    A.C,
    B.C,
    C.C

---

如果您使用的是SQL Server 2005或更高版本，则可以尝试递归CTE：

DECLARE @length int;
SET @length = 3;

WITH expanded AS (
  SELECT
    C = SUBSTRING(@string, N, 1)
  FROM numbers
  WHERE number BETWEEN 1 AND LEN(@string)
),
permutations AS (
  SELECT
    S = CAST(C AS nvarchar(max)),
    L = 1
  FROM expanded
  UNION ALL
  SELECT
    S = S + C,
    L = L + 1
  FROM permutations p
  CROSS JOIN expanded e
  WHERE L < @length
)
SELECT *
FROM permutations
WHERE L = @length
;

其中n是0到32767之间的整数值，表示递归CTE的最大迭代次数，上面提到的100是默认值。Nil实际上意味着没有限制，应该谨慎使用

---

您可以尝试此查询并使用它，我将@字符串减少为仅8个字符，以便能够为@length指定更多不同的值，而无需使查询返回太多行，并且还将numbers表定义为a的子集。

在收到与可能的排列数量相关的注释后，我意识到对字符集的长度以及指定的长度应该有非常严格的限制

考虑到允许的长度非常小，我认为在脚本中使用条件没有什么害处。。。像这样：

DECLARE
    @string NVARCHAR(40), --limit the length of the character set to 40
    @length INT -- the limit for this is in a validation check below

SELECT
    @string = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ',
    @length = 2



IF (@length < 1 OR @length > 4) BEGIN
    RAISERROR('Invalid length specified. This function only supports lengths from 1 to 4', 16, 1)
END



DECLARE @Chars TABLE (
    C CHAR(1) PRIMARY KEY
)

;WITH numbers AS (
    SELECT TOP(LEN(@string)) number
    FROM master..spt_values
    WHERE type = 'P'
    AND number != 0
)

INSERT @Chars (
    C
)
SELECT
    C = SUBSTRING(@string, number, 1)
FROM numbers


IF (@length = 1) BEGIN
    SELECT C FROM @Chars ORDER BY C
END ELSE IF (@length = 2) BEGIN
    SELECT A.C + B.C
    FROM @Chars A, @Chars B
    ORDER BY A.C, B.C
END ELSE IF (@length = 3) BEGIN
    SELECT A.C + B.C + C.C
    FROM @Chars A, @Chars B, @Chars C
    ORDER BY A.C, B.C, C.C
END ELSE IF (@length = 4) BEGIN
    SELECT A.C + B.C + C.C + D.C
    FROM @Chars A, @Chars B, @Chars C, @Chars D
    ORDER BY A.C, B.C, C.C, D.C
END

---

是否要将排列作为包含单个字符的列返回？这意味着列数可变，而这又意味着动态脚本。一个包含指定长度字符串的单列可以吗？@AndriyM:可以。我也编辑了我的问题来说明这一点。谢谢。+1使用笛卡尔积生成排列，非常聪明，但一旦达到10+位数，这将对数据库造成负担…如果字符集始终为36个字符，则可以计算排列的数量，然后创建从0到n的排列，从10到36，用零填充左边。前几天我刚做了这个-但是对于一个给定的整数-不是一系列的整数。。。从base10到base36转换角度接近它并不难。。。固定注释，将26个字符更改为3636个字符@4位数=1.7Mil排列；5位=60Mil；6位数字=2.2比尔；等等。字符集中的字符和数字的上限是多少？这个解决方案确实有效，但我不喜欢它生成长度等于或小于指定长度的所有排列。随着指定长度和/或字符集长度的增长。。。。这不能很好地扩展。

DECLARE
    @string NVARCHAR(40), --limit the length of the character set to 40
    @length INT -- the limit for this is in a validation check below

SELECT
    @string = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ',
    @length = 2



IF (@length < 1 OR @length > 4) BEGIN
    RAISERROR('Invalid length specified. This function only supports lengths from 1 to 4', 16, 1)
END



DECLARE @Chars TABLE (
    C CHAR(1) PRIMARY KEY
)

;WITH numbers AS (
    SELECT TOP(LEN(@string)) number
    FROM master..spt_values
    WHERE type = 'P'
    AND number != 0
)

INSERT @Chars (
    C
)
SELECT
    C = SUBSTRING(@string, number, 1)
FROM numbers


IF (@length = 1) BEGIN
    SELECT C FROM @Chars ORDER BY C
END ELSE IF (@length = 2) BEGIN
    SELECT A.C + B.C
    FROM @Chars A, @Chars B
    ORDER BY A.C, B.C
END ELSE IF (@length = 3) BEGIN
    SELECT A.C + B.C + C.C
    FROM @Chars A, @Chars B, @Chars C
    ORDER BY A.C, B.C, C.C
END ELSE IF (@length = 4) BEGIN
    SELECT A.C + B.C + C.C + D.C
    FROM @Chars A, @Chars B, @Chars C, @Chars D
    ORDER BY A.C, B.C, C.C, D.C
END