SQL Server

Compress and Decompress a String

See more Compression Examples

Demonstrates how to compress and decompress a string. SQL Server

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    -- This example assumes the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

    DECLARE @sb int
    EXEC @hr = sp_OACreate 'Chilkat.StringBuilder', @sb OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    DECLARE @i int

    SELECT @i = 1
    WHILE @i <= 20
      BEGIN
        EXEC sp_OAMethod @sb, 'Append', @success OUT, 'This is the original uncompressed string.' + CHAR(13) + CHAR(10)
        SELECT @i = @i + 1
      END

    DECLARE @compress int
    EXEC @hr = sp_OACreate 'Chilkat.Compression', @compress OUT

    EXEC sp_OASetProperty @compress, 'Algorithm', 'deflate'
    -- Indicate that the utf-8 byte representation of the string should be compressed.
    EXEC sp_OASetProperty @compress, 'Charset', 'utf-8'

    EXEC sp_OAMethod @sb, 'GetAsString', @sTmp0 OUT
    EXEC sp_OAMethod @compress, 'CompressString', @compressedBytes OUT, @sTmp0

    -- If the compressed data is desired in string format, then get the base64 representation of the bytes.
    EXEC sp_OASetProperty @compress, 'EncodingMode', 'base64'
    DECLARE @compressedBase64 nvarchar(4000)
    EXEC sp_OAMethod @sb, 'GetAsString', @sTmp0 OUT
    EXEC sp_OAMethod @compress, 'CompressStringENC', @compressedBase64 OUT, @sTmp0

    PRINT 'Compressed Bytes as Base64: ' + @compressedBase64

    -- Now decompress...
    DECLARE @decompressedString nvarchar(4000)
    EXEC sp_OAMethod @compress, 'DecompressString', @decompressedString OUT, @compressedBytes

    PRINT 'The original string after decompressing from binary compressed data:'

    PRINT @decompressedString

    -- To decompress from Base64...
    EXEC sp_OASetProperty @compress, 'EncodingMode', 'base64'
    EXEC sp_OAMethod @compress, 'DecompressStringENC', @decompressedString OUT, @compressedBase64

    PRINT 'The original string after decompressing from Base64:'

    PRINT @decompressedString

    EXEC @hr = sp_OADestroy @sb
    EXEC @hr = sp_OADestroy @compress


END
GO