Retrieve varbinary value as BASE64 in MSSQL

Question

I\'m looking for a way for retrieving Entity Data Model (EDM) from __MigrationHistory table using only T-SQL (so anyone, using Microsoft SQL Se

Answer 1

Necromancing.
You can also use for JSON PATH similar to how for XML PATH is used:

SELECT 
     T_AP_Dokumente.DK_UID 
    ,T_AP_Dokumente.DK_Thumbnail 
    ,tBase64.JSON_Thumbnail 
    ,NULLIF(T.XML_Thumbnail, '') AS base64  


    ,COMPRESS(T_AP_Dokumente.DK_Thumbnail) AS gzipped 
    ,DATALENGTH(COMPRESS(T_AP_Dokumente.DK_Thumbnail)) AS dlt_datalength_gzipped 
    ,DATALENGTH(T_AP_Dokumente.DK_Thumbnail) AS dlt_datalength 
    ,DATALENGTH(DECOMPRESS(COMPRESS(T_AP_Dokumente.DK_Thumbnail))) AS should_equal_dlt_datalength 
FROM T_AP_Dokumente 

CROSS APPLY 
(
    SELECT T_AP_Dokumente.DK_Thumbnail AS '*' FOR XML PATH('')
) AS T(XML_Thumbnail)

CROSS APPLY 
(
    SELECT * FROM 
    OPENJSON 
    (
        (
            SELECT T_AP_Dokumente.DK_Thumbnail AS JSON_Thumbnail 
            FOR JSON PATH 
        )
    ) WITH(JSON_Thumbnail varchar(MAX)) AS t 
) AS tBase64 

Answer 2

Finally found this article:

https://social.technet.microsoft.com/wiki/contents/articles/36388.transact-sql-convert-varbinary-to-base64-string-and-vice-versa.aspx#Convert_VARBINARY_to_Base64_String

So, running the query gets what I wanted, valid Base64.

Using XML and the hint "for xml path"

select Model, baze64
from __MigrationHistory
cross apply (select Model as '*' for xml path('')) T (baze64)

Other presented queries in article will also work

Using XML XQuery

Using JSON

Answer 3

It's apparently gzip'd xml. eg

SELECT MigrationId
      ,ContextKey
      ,cast(decompress(model) as xml) model
  FROM __MigrationHistory

Answer 4

You can Convert binary to Base64 using XML and the hint "for xml path"

select Column1,ColumnWithBinary,ColumnToSwFinalResult
from TableWithBinary
cross apply (select ColumnWithBinaryas '*' for xml path('')) T (ColumnToSwFinalResult)
GO