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Databases, Blob - How do I access?

Posted on 1998-08-27
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Last Modified: 2010-04-10
How can I access my Blob Field I created.  I want to store/retrieve 1024 Bytes.  But I just seem to be too clumsy too store or retrieve anything from it (newbie-experience).

I'm working with C++B 3 on a Paradox 7 Table.

Thx
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Question by:Odie
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7 Comments
 
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Expert Comment

by:duneram
ID: 1171438
I use the Borland Database Engine.  Get your hands on a copy of it.  It comes with the api and documentation for you to build classes for tables so you can get and put to a blob in a painless manner.  try www.inprise.com

Go to http://www.inprise.com/searchsite/
and enter 'Frameworks'  and check the Borland Database Engine checkbox

Then press search.
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Expert Comment

by:duneram
ID: 1171439
Another decent reference at that site:

http://www.inprise.com/devsupport/bde/cppfiles.html
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Author Comment

by:Odie
ID: 1171440
Um...  I should have mentioned that I'm using the BDE too.  But I'm too stupid too handle the TBlobField.

MyTable->FieldByName("MyBlobField")->...

then what do I do with this?
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by:duneram
ID: 1171441
I'll look into it!!  Do you use the frameworks code generator?
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Author Comment

by:Odie
ID: 1171442
I don't know what it is.  (Guess I don't then.)
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Expert Comment

by:duneram
ID: 1171443
I'll take a look this weekend...  oh i forgot I am going to be out of town this weekend. I guess I have to wait until monday.  HOpefully someone else will beat me and post your answer here.

In the mean time take a look at any of these functions in your documentation:

DbiAppendRecord: Appends a record to the end of the table associated with the given cursor.
DbiDeleteRecord: Deletes the current record of the given cursor.
DbiFreeBlob: Closes the BLOB handle located within the specified record buffer.
DbiGetBlob: Retrieves data from the specified BLOB field.
DbiGetBlobHeading: Retrieves information about a BLOB field from the BLOB heading in the record buffer.
DbiGetBlobSize: Retrieves the size of the specified BLOB field in bytes.
DbiGetField: Retrieves the data contents of the requested field from the record buffer.
DbiGetFieldDescs: Retrieves a list of descriptors for all the fields in the table associated with the cursor.
DbiGetFieldTypeDesc: Retrieves a description of the specified field type.
DbiInitRecord: Initializes the record buffer to a blank record according to the data types of the fields.
DbiInsertRecord: Inserts a new record into the table associated with the given cursor.
DbiModifyRecord: Modifies the current record of table associated with the cursor with the data supplied.
DbiOpenBlob: Prepares the cursor's record buffer to access a BLOB field.
DbiPutBlob: Writes data into an open BLOB field.
DbiPutField: Writes the field value to the correct location in the supplied record buffer.
DbiReadBlock: Reads a specified number of records (starting from the next position of the  cursor) into a buffer.
DbiSaveChanges: Forces all updated records associated with the cursor to disk.
DbiSetFieldMap: Sets a field map of the table associated with the given cursor.
DbiTruncateBlob: Shortens the size of the contents of a BLOB field, or deletes the contents of a BLOB field from the record, by shortening it to zero.
DbiUndeleteRecord: Undeletes a dBASE record that has been marked for deletion (a "soft"  delete).
DbiVerifyField: Verifies that the data specified is a valid data type for the field specified, and that all validity checks in place for the field are satisfied. It can also be used to check if a field is  blank.
DbiWriteBlock: Writes a block of records to the table associated with the cursor.


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Accepted Solution

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cph earned 100 total points
ID: 1171444
You can only read/write and do some basic file operation on a BLOB as the DB doesn't know anything about its content. What you could do is set a field in your table run an SQL query based on that field then retrieve it.

Hope this help,

CpH
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