my application datbase in postgressql and from the document i understand that it store few data in a blob and from the table i can only get the oid of it.
is there any possibility to read the content from these blobs? if yes, could someone share the knowhow?
From the OID, a file with the contents of the large object can be exported.
Either client-side (psql):
\lo_export oid-to-export /path/to/a/file
Or server-side in SQL (creates the file on the server, beware that postgres must have the permission to write into the destination directory).
SELECT lo_export(oid-to-export, '/path/to/a/file');
Related
My problem statement is that I have a csv blob and I need to import that blob into a sql table. Is there an utility to do that?
I was thinking of one approach, that first to copy blob to on-premise sql server using AzCopy utility and then import that file in sql table using bcp utility. Is this the right approach? and I am looking for 1-step solution to copy blob to sql table.
Regarding your question about the availability of a utility which will import data from blob storage to a SQL Server, AFAIK there's none. You would need to write one.
Your approach seems OK to me. Though you may want to write a batch file or something like that to automate the whole process. In this batch file, you would first download the file on your computer and the run the BCP utility to import the CSV in SQL Server. Other alternatives to writing batch file are:
Do this thing completely in PowerShell.
Write some C# code which makes use of storage client library to download the blob and once the blob is downloaded, start the BCP process in your code.
To pull a blob file into an Azure SQL Server, you can use this example syntax (this actually works, I use it):
BULK INSERT MyTable
FROM 'container/folder/folder/file'
WITH ( DATA_SOURCE = 'ds_blob',BATCHSIZE=10000,FIRSTROW=2);
MyTable has to have identical columns (or it can be a view against a table that yields identical columns)
In this example, ds_blob is an external data source which needs to be created beforehand (https://learn.microsoft.com/en-us/sql/t-sql/statements/create-external-data-source-transact-sql)
The external data source needs to use a database contained credential, which uses an SAS key which you need to generate beforehand from blob storage https://learn.microsoft.com/en-us/sql/t-sql/statements/create-database-scoped-credential-transact-sql)
The only downside to this mehod is that you have to know the filename beforehand - there's no way to enumerate them from inside SQL Server.
I get around this by running powershell inside Azure Automation that enumerates blobds and writes them into a queue table beforehand
I want to store large files in SQL Server 2012. I have been suggested to use BLOB. All I want to do is to create a table which map the Employee id and the path of his image in database. Whenever user want to access the image he will get the path from the database first and then get the image from referenced database using BLOB.
Can you help me how to access different database from one database.
Generally speaking for large files (over 1 MB, but not a rule) you should use FILESTREAM (Overview) which stores the files on filesystem and not in the database itself.
See this article for a guide to set up using FILESTREAM in your database.
As for your question "Can you help me how to access different database from one database." Referencing objects in SQL is done with dot notation like this
databasename.schemaname.tablename
So you can use it to reference objects (tables) in different databases. For more info see Using Identifiers As Object Names not to reiterate what's there already.
I have a table named Reports which has 3 fields ID (auto number), filename (string field), theFile (attachment field).
What I want to is to run a SQL query and insert a PDF file into the attachments field (theFile).
Lets say the PDF file is located in the C: drive (C:\report1.pdf), I have tried the SQL query below but it is not working. I know its not good practice to store files in a database but I just want to try it out:
CurrentDb.Execute "INSERT INTO Reports (filename,theFile) VALUES ('report1'," & C:\report1.pdf & ")"
It's standard practice to store files in a database. Access certainly supports it, but not through SQL. You'll have to use DAO, as detailed at http://msdn.microsoft.com/en-us/library/office/bb258184%28v=office.12%29.aspx
"File" is not appropriate SQL data type supported in Access, available data types.
That is correct Derek, if you try to run a SQL statement like that you will get an error message of one type or another every time. I spent a fair amount of time researching this subject for my own DB, and from what I understand there are a number of options/alternatives; however, having an attachment column type and using SQL to insert a file is not an option with Access' current capabilities.
It is not bad practice to store files in a database, it is actually standard practice; however, it IS best practice to not store files in an ACCESS db. There are a few reasons for this which you can research on your own, but perhaps most notably, Access has a file size limit of 2GB, so if you store files in it you can run out of space quickly and then things get even more complicated.
Here are your options:
Change your column data type to OLE object and use some kind of stream reader to convert the files to binary data, then use a SQL statement to load them into your DB
Use the built in Access user interface for working directly with tables/attachments
Establish a DAO db connection and use Access' recordset.LoadFromFile function
Just store links to the files in the Access DB
The 4th option is the preferred method. It's very simple and you won't have to worry about complex code or the 2GB storage limit.
I have created filestream group at C:\Test\FilestreamGroup1
and a table with varBinary Filstream column
Now when file is uploaded then it physically stored at FilestreamGroup1...
Now here I want to know two things
In which format file is stored at FilestreamGroup1 (for every single uploaded file I found 2 encoded file)?
secondly how to delete uploaded file physically (i.e. deleting a record from the table is like execute delete command, but doing this I'll not result in physical deletion of file from NTFS...so how can I delete a file physically)
If you want to delete files from FileSystem instanly then you need to force garbage collection manually by using checkpoint
Link
This is not a StackOverflow question, this belongs to ServerFault (admin). It toucehs dev though-
i.e. deleting a record from the table is like execute delete command, but doing this I'll not result in physical
deletion of file from NTFS...so how can I delete a file physically
Do you know what the primary reason is to hav a database? Guarantee data integrity.
A delete must keep the data around until a backup is taken. What is your backup policy? YOU may note that when you make an update, another copy of the file is created.... for that simple reason. The old one must still b e available for backup, and that is just how they integrate it.
In which format file is stored at FilestreamGroup1 (for every single uploaded file I found 2 encoded file)?
No, files are stored raw. What would be the sense to encode them... if there are SQL functions to get the path and it is a supported scenario that the client does not use SQL to load the file (but: asks SQL for the file name and path, then accesses it via NTFS file share). This also supports interop (as any program loading from a network can be fed a SQL driven location.
I strongly assume you have 1 copy only and somehow make an update resulting in a second file written.
http://msdn.microsoft.com/en-us/library/cc645962.aspx
has an explanation how to access FileSTream data with SQL.
http://technet.microsoft.com/en-us/library/cc645940(v=sql.105).aspx
has an explanation how to access FIleStream data using Win32.
FILESTREAM files being left behind after row deleted
explains while files are left behind when a row is deleted. I found that using the extremely trivial goodle search for "sql filestream delete file" and it was item 1 on the result list - did you even try google?
secondly how to delete uploaded file physically (i.e. deleting a record from the table is like execute delete command, but doing this I'll not result in physical deletion of file from NTFS...so how can I delete a file physically)
Checkpoint does not remove the files, files are removed in a backgroundprocess and it can take quite a while. To force deletion use
sp_filestream_force_garbage_collection
EDIT: works with SQL Server 2012 only
Write "checkpoint" after deleting a row. it will remove physical existence of file.
Run the below query and check, the file getting deleted from file system automatically
DELETE FROM TableName CHECKPOINT
Thanks.
I can not find useful code for how storing the images into BLOB ,please help me with some code and also can I show those images from MySQL to my desktop pane in GUI?
If the image is located on your MySQL host, you could use the LOAD_FILE() command for storing an image in a BLOB:
-- Using the following table as an example:
CREATE TABLE MyTable (
image BLOB
);
-- This will insert a file in a BLOB column.
INSERT INTO MyTable (image) VALUES(LOAD_FILE('/tmp/image.png'));
Make sure that the image file is readable by MySQL, and also make sure that your MySQL user has the FILE privilege.
To grant the FILE privilege, log-in as root and execute:
GRANT FILE ON *.* TO 'mysql_user'#'localhost';
Easiest way is to store the contents of some binary image file in the blob, extract them, write them to a file and open that file with an image file parser of some kind. Or, if you're really tricky, use that same image parser to read the data from memory directly after pulling the blob out of the DB.
I'm assuming you've got some sort of ImagePane widget that can handle the GUI display if you can provide an image file to it.