Um Checksummen im MS SQL Umfeld zu berechnen gibt es folgende Möglichkeiten:

Allgemeines

Bei Checksum scheint es sich um einen CRC32 Hash zu handeln. (vgl. hier). Wer aber auf Nummer sicher gehen will, kann die unten angeführte und in dieser Diskussion entwickelten Funktionen verwenden. Ich persönlich verwende weder die Checksum-Funktion, die ab SQL Server Server 2005 integriert ist, noch die unten angeführten Funktionen, da CRC32 keine unerhebliche Gefahr von Hash-Collisionen hat.

Seit SQL Server 2005 gibt es neben der Checksum die HASHBYTE Funktion, die sukzessive erweitert wurde und mit SQL Server 2016 die Algorithmen SHA2_256 und SHA2_512 erhalten hat. Seither sind alte Funktionen deprecated (dh. sie sollen nicht mehr verwendet werden). Somit geht meine Empfehlung in Bezug auf Checksummen entweder SHA_256, SHA2_512 (vgl hier). In diesem Zusammenhang ist zu erwähnen, dass bis SQL Server 2014 der Input auf 8000 bytes begrenzt war.

Während Checksum die Übergabe mehrere Spalten ermöglicht, erlaubt HASHBYTE nur eine Spalte.
> Select Checksum(Spalte1,Spalte2) as [CRC32]

Bei HASHBYTES muss man ein paar Tricks anwenden, um eine Checksumme über mehrere Spalten zu erzeugen. Allen ist gemeinsam, dass die Spalten irgendwie verbunden werden.

Möglichkeit 1: CONCAT
HASHBYTES(‚SHA2_256′, CONCAT(col1,’|‘,col2,’|‘,col3))
HASHBYTES(‚SHA2_256‘, CONCAT_WS(‚|‘,col1,col2,col3))

Möglichkeit 2: XML
HASHBYTES(‚MD5‘, (SELECT Icol1,col2,col3 FOR XML RAW))
HASHBYTES(‚MD5‘, (SELECT Icol1,col2,col3 FOR XML AUTO))

T-SQL CRC32 Functions

Quelle: https://stackoverflow.com/questions/331157/does-sql-server-checksum-calculate-a-crc-if-not-how-can-i-get-ms-sql-to-calcula

CREATE FUNCTION dbo.IndexTable
(
      @FirstIndex           bigint
    , @LastIndex            bigint
)
RETURNS @Result table
(
    Id BIGINT PRIMARY KEY
)
WITH SCHEMABINDING
AS
/***************************************************************************************************
    DESCRIPTION:
         Create an one column table of indexes starting with first specified index and 
         ending with last specified index.

    INPUT PARAMETERS:
         @FirstIndex:    First index to start the list of indexes with.
         @LastIndex:     Last index to end the list of indexes with.

    RETURN VALUE:
         Table with list of specified indexes.

    EXAMPLES:
        SELECT * FROM dbo.IndexTable(1, 20)
        SELECT * FROM dbo.IndexTable(1, 16)
        SELECT * FROM dbo.IndexTable(1, 17)
        SELECT * FROM dbo.IndexTable(1, 18)
        SELECT * FROM dbo.IndexTable(1, 1)
        SELECT * FROM dbo.IndexTable(1, 0)
***************************************************************************************************/
BEGIN
    DECLARE @max        bigint
    ,       @offset     bigint
    ;
    IF @LastIndex IS NULL RETURN ;
    IF @FirstIndex IS NULL RETURN ;
    INSERT INTO @Result 
    VALUES  (@FirstIndex+0), (@FirstIndex+1), (@FirstIndex+2), (@FirstIndex+3), (@FirstIndex+4)
    ,       (@FirstIndex+5), (@FirstIndex+6), (@FirstIndex+7), (@FirstIndex+8), (@FirstIndex+9)
    ;
    SELECT @max= MAX(Id) FROM @Result
    ;
    WHILE @max < @LastIndex
    BEGIN
        SET @offset = (1 + @max - @FirstIndex)
        ;
        INSERT
        INTO    @Result
        SELECT  Id = Id + @offset
        FROM    @Result
        WHERE   Id <= (@LastIndex - @offset)
        ;
        SELECT @max= MAX(Id) FROM @Result
        ;
    END
    DELETE FROM @Result WHERE Id > @LastIndex
    ;
    RETURN
END
GO

CREATE FUNCTION dbo.CRC32calc
/***************************************************************************************************
    DESCRIPTION
        Add a byte value to a CRC calculation.

    INPUT PARAMETERS:
        @crc            Current CRC value.
        @byteval        Byte value to add to CRC value.

    RETURN VALUE:
        Resulting CRC with bytevalue added.

    USAGE:
        Used by functions dbo.CRC32 and dbo.NCRC32
***************************************************************************************************/
(
    @crc        bigint,
    @byteval    int
)
RETURNS bigint
WITH SCHEMABINDING
AS
BEGIN
    DECLARE @Lookup     varbinary(2048) = 0x0000000077073096EE0E612C990951BA076DC419706AF48
FE963A5359E6495A30EDB883279DCB8A4E0D5E91E97D2D98809B64C2B7EB17CBDE7B82D0790BF1D911DB710646A
B020F2F3B9714884BE41DE1ADAD47D6DDDE4EBF4D4B55183D385C7136C9856646BA8C0FD62F97A8A65C9EC14015
C4F63066CD9FA0F3D638D080DF53B6E20C84C69105ED56041E4A26771723C03E4D14B04D447D20D85FDA50AB56B
35B5A8FA42B2986CDBBBC9D6ACBCF94032D86CE345DF5C75DCD60DCFABD13D5926D930AC51DE003AC8D75180BFD
0611621B4F4B556B3C423CFBA9599B8BDA50F2802B89E5F058808C60CD9B2B10BE9242F6F7C8758684C11C1611D
ABB6662D3D76DC419001DB710698D220BCEFD5102A71B1858906B6B51F9FBFE4A5E8B8D4337807C9A20F00F9349
609A88EE10E98187F6A0DBB086D3D2D91646C97E6635C016B6B51F41C6C6162856530D8F262004E6C0695ED1B01
A57B8208F4C1F50FC45765B0D9C612B7E9508BBEB8EAFCB9887C62DD1DDF15DA2D498CD37CF3FBD44C654DB2615
83AB551CEA3BC0074D4BB30E24ADFA5413DD895D7A4D1C46DD3D6F4FB4369E96A346ED9FCAD678846DA60B8D044
042D7333031DE5AA0A4C5FDD0D7CC95005713C270241AABE0B1010C90C20865768B525206F85B3B966D409CE61E
49F5EDEF90E29D9C998B0D09822C7D7A8B459B33D172EB40D81B7BD5C3BC0BA6CADEDB883209ABFB3B603B6E20C
74B1D29AEAD547399DD277AF04DB261573DC1683E3630B1294643B840D6D6A3E7A6A5AA8E40ECF0B9309FF9D0A0
0AE277D079EB1F00F93448708A3D21E01F2686906C2FEF762575D806567CB196C36716E6B06E7FED41B7689D32B
E010DA7A5A67DD4ACCF9B9DF6F8EBEEFF917B7BE4360B08ED5D6D6A3E8A1D1937E38D8C2C44FDFF252D1BB67F1A
6BC57673FB506DD48B2364BD80D2BDAAF0A1B4C36034AF641047A60DF60EFC3A867DF55316E8EEF4669BE79CB61
B38CBC66831A256FD2A05268E236CC0C7795BB0B4703220216B95505262FC5BA3BBEB2BD0B282BB45A925CB36A0
4C2D7FFA7B5D0CF312CD99E8B5BDEAE1D9B64C2B0EC63F226756AA39C026D930A9C0906A9EB0E363F7207678505
00571395BF4A82E2B87A147BB12BAE0CB61B3892D28E9BE5D5BE0D7CDCEFB70BDBDF2186D3D2D4F1D4E24268DDB
3F81FDA836E81BE16CDF6B9265B6FB077E118B7477788085AE6FF0F6A7066063BCA11010B5C8F659EFFF862AE69
616BFFD3166CCF45A00AE278D70DD2EE4E0483543903B3C2A7672661D06016F74969474D3E6E77DBAED16A4AD9D
65ADC40DF0B6637D83BF0A9BCAE53DEBB9EC547B2CF7F30B5FFE9BDBDF21CCABAC28A53B3933024B4A3A6BAD036
05CDD7069354DE572923D967BFB3667A2EC4614AB85D681B022A6F2B94B40BBE37C30C8EA15A05DF1B2D02EF8D;
    RETURN (@crc / 256) ^ Substring(@Lookup, ((@crc & 0xFF) ^ @byteval) * 4 + 1, 4)
    ;
END
GO

CREATE FUNCTION dbo.CRC32
/***************************************************************************************************
    DESCRIPTION
        Compute 32-bit CRC from an ASCII character array.

    INPUT PARAMETERS:
        @input          ASCII text to compute CRC for.

    RETURN VALUE:
        Resulting 32-bit CRC value.

    EXAMPLES:
        SELECT  t.input, csum = CHECKSUM(t.input), t.crc, crchex = CONVERT(VARBINARY(8), t.crc)
        FROM    (   SELECT  t.input, crc = dbo.CRC32(t.input)
                    FROM    (         SELECT  input = 'test'
                                UNION SELECT  input = 'x'
                                UNION SELECT  input = ''
                                UNION SELECT  input = NULL
                                UNION SELECT  input = 'stop'
                                UNION SELECT  input = 'pots'
                                UNION SELECT  input = 'System.IO.Stream'
                                UNION SELECT  input = 'SYSTEM.IO.Stream'
                                UNION SELECT  input = 'Test.fqn.data'
                                UNION SELECT  input = 'Test.fqn.datax'
                            ) AS t
                ) AS t
***************************************************************************************************/
(
    @input varchar(max)
)
RETURNS int
WITH SCHEMABINDING
AS
BEGIN
    DECLARE @crc        bigint = 0xFFFFFFFF
    ,       @result     int
    ;
    SELECT @crc = dbo.CRC32calc(@crc, Ascii(Substring(@input, v.id, 1)))
    FROM    dbo.IndexTable(1, LEN(@input)) AS v
    ORDER
    BY      v.Id
    ;
    SET @result = CONVERT(int, CONVERT(VARBINARY(4), ~@crc)) ;
    RETURN @result ;
END
GO

CREATE FUNCTION dbo.NCRC32
/***************************************************************************************************
    DESCRIPTION
        Compute 32-bit CRC from a UNICODE character array.

    INPUT PARAMETERS:
        @input          ASCII text to compute CRC for.

    RETURN VALUE:
        Resulting 32-bit CRC value.

    EXAMPLES:
        SELECT  t.input, csum = CHECKSUM(t.input), t.crc, crchex = CONVERT(VARBINARY(8), t.crc)
        FROM    (   SELECT  t.input, crc = dbo.NCRC32(t.input)
                    FROM    (         SELECT  input = N'test'
                                UNION SELECT  input = N'x'
                                UNION SELECT  input = N''
                                UNION SELECT  input = NULL
                                UNION SELECT  input = 'stop'
                                UNION SELECT  input = 'pots'
                                UNION SELECT  input = N'System.IO.Stream'
                                UNION SELECT  input = N'SYSTEM.IO.Stream'
                                UNION SELECT  input = N'Test.fqn.data'
                                UNION SELECT  input = N'Test.fqn.datax'
                            ) AS t
                ) AS t
***************************************************************************************************/
(
    @input nvarchar(max)
)
RETURNS int
WITH SCHEMABINDING
AS
BEGIN
    DECLARE @crc        bigint = 0xFFFFFFFF
    ,       @result     int
    ;
    SELECT  @crc = dbo.CRC32calc( dbo.CRC32calc(@crc, (cval / 256)), cval & 0xFF)
    FROM    (   SELECT  v.id, cval = UNICODE(SUBSTRING(@input, v.id, 1))
                FROM    dbo.IndexTable(1, LEN(@input)) AS v
            ) AS t
    ORDER
    BY      t.Id
    ;
    SET @result = CONVERT(int, CONVERT(VARBINARY(4), ~@crc)) ;
    RETURN @result ;
END
GO

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