BLOBs are db specific, I am afraid, so the only generalization you'll find is the DBI.
The Super Search will tell you what is already in the pot.

At your shell prompt, type

perldoc DBI
[download]

and search for "BLOB". There are some interesting points.

For some inspiration on how to do it with MySQL, check this node.

A database independent alternative is to store the images in external files, and have only the file name in your database. It is not my favorite solution, but you can find more on this subject at these nodes.

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