반복없는 조합에 대한 SQL 쿼리


22

함수에 사용되거나 함수로 사용할 수 있고 n 값의 모든 조합을 검색하는 쿼리가 필요합니다. 그리고 k = 1..n 인 길이 k의 모든 조합이 필요합니다.

확장 된 샘플 입력 및 결과이므로 입력에는 2 대신 3 개의 값이 있지만 입력 값의 수는 1에서 n까지 다양합니다.

예 : 입력 : 여러 행의 한 열에 값이있는 테이블

Value  (nvarchar(500))
------
Ann
John
Mark

출력 # 1 : 하나의 열에 연결된 값이있는 테이블

    Ann
    John
    Mark
    Ann,John
    John,Mark
    Ann,Mark
    Ann,John,Mark

답변:


36

비교적 작은 값 n(이 예에서는 20)의 경우 자연 정수가 비트의 조합이라는 사실을 이용하는 방법을 사용할 수 있습니다.

T-SQL 솔루션

샘플 데이터 :

DECLARE @Sample AS TABLE 
(
    item_id     tinyint IDENTITY(1,1) PRIMARY KEY NONCLUSTERED,
    item        nvarchar(500) NOT NULL,
    bit_value   AS 
                CONVERT
                (
                    integer, 
                    POWER(2, item_id - 1)
                )
                PERSISTED UNIQUE CLUSTERED
);    

INSERT @Sample
    (item)
VALUES
    (N'Ann'),
    (N'Bob'),
    (N'Charles'),
    (N'Darren'),
    (N'Eric'),
    (N'Fred'),
    (N'George'),
    (N'Harry'),
    (N'Ian'),
    (N'John'),
    (N'Keith'),
    (N'Larry'),
    (N'Mark'),
    (N'Nathan'),
    (N'Owen'),
    (N'Paul'),
    (N'Quentin'),
    (N'Ryan'),
    (N'Steve'),
    (N'Terry');

해결책:

-- Maximum integer we need
-- for all combinations of 'n' bits
DECLARE 
    @max integer = 
    POWER(2,
        (
            SELECT COUNT(*) 
            FROM @Sample AS s
        )
    ) - 1;

SELECT
    combination =
        STUFF
        (
            (
                -- Choose items where the bit is set
                -- and concatenate all matches
                SELECT ',' + s.item 
                FROM @Sample AS s
                WHERE
                    n.n & s.bit_value = s.bit_value
                ORDER BY
                    s.bit_value
                FOR XML 
                    PATH (''),
                    TYPE                    
            ).value('(./text())[1]', 'varchar(8000)'), 1, 1, ''
        )
-- A standard numbers table
-- (single column, integers from 1 to 1048576, indexed)
FROM dbo.Numbers AS N
WHERE
    N.n BETWEEN 1 AND @max;

출력 샘플 :

╔════════════════════════╗
      combination       
╠════════════════════════╣
 Ann                    
 Bob                    
 Ann,Bob                
 Charles                
 Ann,Charles            
 Bob,Charles            
 Ann,Bob,Charles        
 Darren                 
 Ann,Darren             
 Bob,Darren             
 Ann,Bob,Darren         
 Charles,Darren         
 Ann,Charles,Darren     
 Bob,Charles,Darren     
 Ann,Bob,Charles,Darren 
 ...                    
╚════════════════════════╝

실행 계획 :

실행 계획

1,048,576 개의 조합 을 노트북의 변수에 쓰는 데 41 초가 걸립니다 . 강제 병렬 처리를 통해 실행 시간 을 13 초로 단축 할 수있었습니다 .DOP 8

Numbers 테이블이 필요한 경우이를 생성하는 빠른 방법입니다.

SELECT TOP (1048576)
    n = ISNULL(CONVERT(integer, ROW_NUMBER() OVER (ORDER BY (SELECT NULL))), 0)
INTO dbo.Numbers
FROM sys.columns AS c
CROSS JOIN sys.columns AS c2
CROSS JOIN sys.columns AS c3;

CREATE UNIQUE CLUSTERED INDEX cuq
ON dbo.Numbers (n)
WITH (MAXDOP = 1, SORT_IN_TEMPDB = ON);

SQLCLR 솔루션

SQLCLR에서 훨씬 더 효율적인 구현이 가능합니다 (SQL Server 2005 이후).

CREATE ASSEMBLY [Demo]
    AUTHORIZATION [dbo]
    FROM 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GO
CREATE FUNCTION dbo.Combinations
(
    @ElementsCSV nvarchar (4000)
)
RETURNS TABLE
(
    Combination nvarchar (4000) NULL
)
AS EXTERNAL NAME Demo.UserDefinedFunctions.Permute;

사용법 예 :

SELECT 
    f.Combination
FROM dbo.Combinations('A,B,C,D') AS f;

산출:

╔═════════════╗
 Combination 
╠═════════════╣
 A           
 B           
 A,B         
 C           
 A,C         
 B,C         
 A,B,C       
 D           
 A,D         
 B,D         
 A,B,D       
 C,D         
 A,C,D       
 B,C,D       
 A,B,C,D     
╚═════════════╝

이전의 20 개 요소 집합 사용 :

DECLARE @Sample AS TABLE 
(
    item_id     tinyint IDENTITY(1,1) PRIMARY KEY CLUSTERED,
    item        nvarchar(50) NOT NULL
);

INSERT @Sample
    (item)
VALUES
    (N'Ann'),
    (N'Bob'),
    (N'Charles'),
    (N'Darren'),
    (N'Eric'),
    (N'Fred'),
    (N'George'),
    (N'Harry'),
    (N'Ian'),
    (N'John'),
    (N'Keith'),
    (N'Larry'),
    (N'Mark'),
    (N'Nathan'),
    (N'Owen'),
    (N'Paul'),
    (N'Quentin'),
    (N'Ryan'),
    (N'Steve'),
    (N'Terry');

SQLCLR 솔루션 :

-- Create CSV input
DECLARE 
    @Elements nvarchar(4000) =
        STUFF
        (
            (
                SELECT ',' + s.item 
                FROM @Sample AS s
                ORDER BY
                    s.item_id
                FOR XML 
                    PATH (''),
                    TYPE                    
            ).value('(./text())[1]', 'varchar(8000)'), 1, 1, ''
        );

DECLARE
    @bitbucket nvarchar(4000);

SELECT
    @bitbucket = combination
FROM dbo.Combinations(@Elements);

내 랩톱에서 1,048,576 개 조합의 실행 시간은 2.5 초 입니다 .DOP 1

CSV 입력 작성 :

CSV 입력 계획

조합 찾기 :

SQLCLR 기능 계획

C # 소스 코드 :

using System;
using System.Collections;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
{
    [SqlFunction
        (
        DataAccess=DataAccessKind.None, 
        SystemDataAccess=SystemDataAccessKind.None,
        FillRowMethodName="FillRow",
        TableDefinition="Permutation nvarchar(4000)"
        )
    ]
    public static IEnumerable Permute(string ElementsCSV)
    {
        // Split CSV
        string[] elements = ElementsCSV.Split(new char[] { ',' });

        // Highest integer needed
        int count = (int)Math.Pow(2, elements.Length) - 1;

        // Pre-computed array of 2^n values
        int[] powers = new int[elements.Length];

        for (int i = 0; i < powers.Length; i++)
        {
            powers[i] = (int)Math.Pow(2, i);
        }

        // Test integers
        for (int i = 1; i <= count; i++)
        {
            // Reset output
            string s = string.Empty;

            // Test each bit that could be set
            for (int bit = 0; bit < powers.Length && i >= powers[bit]; bit++)
            {
                if ((i & powers[bit]) == powers[bit])
                {
                    // Add the element corresponding to the set bit
                    s += elements[bit] + ',';
                }
            }

            // Return a row via enumeration
            yield return s.Substring(0, s.Length - 1);
        }
    }

    // Called by SQL Server to fetch a row
    public static void FillRow(object o, out string Permutation)
    {
        Permutation = (string)o;
    }
}
당사 사이트를 사용함과 동시에 당사의 쿠키 정책개인정보 보호정책을 읽고 이해하였음을 인정하는 것으로 간주합니다.
Licensed under cc by-sa 3.0 with attribution required.