I agree with @andrew and @Harish on this. That said, if did want to look into getting some specific property value out of the BLOB, you can reference the UDFs, in your custom SQL outside of the platform, that are shipped with the product. Note that UDFs are used by report definitions to retrieve un-optimized property value from the BLOB.
I agree with the others and also recommend not using any technology outside of Pega to obtain data from the database; (ie. you could create a custom activity or Report Definition combined with REST service to get the same data and therefore using OOTB Pega functionality to get the data to meet your requirements).
However, to get access to the BLOB in any language, you need to connect to the database and execute an SQL command. If you look at a Pega Report Definition for an unoptimized property, you see will see that Pega generates the SQL to do that. That SQL will give you the "trick" for crafting the SQL;
Again, I don't condone it but I have to admit your requirement may require this solution; of which, I would be interested to see what that requirement is.
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