How store/retrieve BLOB in VB5 and SQl Server7

How store/retrieve BLOB in VB5 and SQl Server7

Post by Vincent Lo » Tue, 19 Jan 1999 04:00:00

I tried to implement by adding in RDO control , I did all the
AppendChunk() & GetChunk(), it seems no changes in SQL Server 7. No
error receive from the server.

1. Edit/Store/Retrieve/Submit SQL Server Blobs via XML

Hi all,

I'm looking for advices about designing a "document server"

application. I'm developing n-tiers solutions in VB and I need to

provide all my applications a way to retrieve, edit and store any

kind of documents as BLOBs in a SQL Database. These documents could

be either Word or Excel Documents, as well as large binary files or

images. I used to do that using "regular" client-server techniques

(ADO recordsets), but now that we've switched to a multi-tier

architecture, the client software does not have any mean to access

ADO methods. Following the strict rules of this architecture, my

client applications know only how to parse a XML document.

I'd like your advice about the following : I've built up a COM+ Data

Object which extracts the data from the BLOB (through a stored

procedure), saves it as XML in a stream (ADO 2.5) and sends it back

to the client as a string. On the client-side, I simply parse this

XML string and extract the "node.typedvalue" for the binary field. I

then decode it and serialize it on the local disk to let the user

access it. It works but I then face two major problems :

1) this way of proceeding is particularly slow and I don't really

see how I could improve it. The size of the XML document generated

by ADO is about twice to third bigger than the original binary file

(due to the non-binary encoding). I could rely on my own algorithms

to extract the BLOB and binary-encode it but I'm affraid it could be

even slower (?).

2) What could be the best way to do the contrary, i.e. upload a

local file to the server to store it into the database ? I was

thinking about finding a good encoding for the data before sending

it to the server as a string, but maybe it's not the most efficient

to way to proceed ?

Has anybody already done that before ? Any idea about the best

encoding / uploading techniques ? Do you see any flaw in the general

architecture I've just described ?

Thx for your helps and advices,


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