Your solution below worked but in the download option i only see save but not open for PDf file in the blob. Please let me know if you have any suggestion to achieve it
Problem providing download link for BLOB data in apex report
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Here is how I have solved this problem.
1. The select statement in the sql for the report should not include the BLOB column. I decided to select only 2 columns, the column that has the key and the column with the filename.
2. On the first column ( the primary key ) I put in the format statement that was simply DOWNLOAD:TABLENAME:BLOB_COLUMN:PRIMARY_KEY
This works. I believe that the Oracle error I was getting was because I was trying to apply this format statement to the actual BLOB column.
So, it appears that you can use any of the columns in the report to hold the DOWNLOAD format statement since in the format statement, you are defining the BLOB table, BLOB column and the primary key into that column.
Hope this helps,