BLOB to String, SQL Server

问题

I have a text string stored as a BLOB data type in a database. I want to extract it by an SQL select query, but I have problems converting/casting from BLOB to readable text.

I've tried e.g.

select convert(nvarchar(40),convert(varbinary(40),BLOBTextToExtract))
from [NavisionSQL$Customer]

I guess I need something similar, but I can't figure out exactly what I need to do the conversion. Can somebody please give me some directions?

Regards

回答1:

Problem was apparently not the SQL server, but the NAV system that updates the field. There is a compression property that can be used on BLOB fields in NAV, that is not a part of SQL Server. So the custom compression made the data unreadable, though the conversion worked.

The solution was to turn off compression through the Object Designer, Table Designer, Properties for the field (Shift+F4 on the field row).

After that the extraction of data can be made with e.g.: select convert(varchar(max), cast(BLOBFIELD as binary)) from Table

Thanks for all answers that were correct in many ways!

回答2:

It depends on how the data was initially put into the column. Try either of these as one should work:

SELECT CONVERT(NVarChar(40), BLOBTextToExtract)
FROM [NavisionSQL$Customer];

Or if it was just varchar...

SELECT CONVERT(VarChar(40), BLOBTextToExtract)
FROM [NavisionSQL$Customer];

I used this script to verify and test on SQL Server 2K8 R2:

DECLARE @blob VarBinary(MAX) = CONVERT(VarBinary(MAX), 'test');

-- show the binary representation
SELECT @blob;

-- this doesn't work
SELECT CONVERT(NVarChar(100), @blob);

-- but this does
SELECT CONVERT(VarChar(100), @blob);

回答3:

The accepted answer works for me only for the first 30 characters. This works for me:

select convert(varchar(max), convert(varbinary(max),myBlobColumn)) FROM table_name

回答4:

Can you try this:

select convert(nvarchar(max),convert(varbinary(max),blob_column)) from table_name

回答5:

Found this...

bcp "SELECT top 1 BlobText FROM TableName" queryout "C:\DesinationFolder\FileName.txt" -T -c'

If you need to know about different options of bcp flags...

http://msdn.microsoft.com/en-us/library/ms162802.aspx

回答6:

CREATE OR REPLACE FUNCTION HASTANE.getXXXXX(p_rowid in rowid) return VARCHAR2
  as
          l_data long;
  begin
         select XXXXXX into l_data from XXXXX where rowid = p_rowid;
         return substr( l_data, 1, 4000);
  end getlabrapor1;

来源：https://stackoverflow.com/questions/6911460/blob-to-string-sql-server

标签

sql

sql-server

blob

dynamics-nav