How you view a BLOB value all depends on your application development platform. SQL*Plus will not let you see BLOB values since SQL*Plus is a text environment and BLOB values are binary data. Also, the BLOB value could be a sound file, or an MPEG movie. SQL*Plus is not able to play sounds or show movies. As such, Oracle has coded SQL*Plus to not show BLOB values.
This Oracle documentation shows a lot of information on BLOBs. Pay close attention to Chapter 6 as it contains information on how to access BLOBs for your specific development platform.
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This was first published in May 2006