I found a script on the web (I haven't tested it, so your mileage may vary)
(of course, you will substitute your own column names and table name
for the ones in this example--the dbms_lob.getlength(column_name)
handles the BLOB columns)

select
3 + avg(nvl(dbms_lob.getlength(blob_column),0)+1 +
nvl(vsize(column1),0)+1 +
nvl(vsize(column2),0)+1 +
nvl(vsize(column3),0)+1
) "Total bytes per row"
from your_table_name;



I am not able to find the way for a table with 3 BLOB datatypes .......
Any suggestions pls ??


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