Hello, 

Can you tell us a bit more about this. Is it a table with a BLOB? What Pega version is it?

To perform this you will have to map the class of the work object to your custom table that you have created.

Configure/Designer Studio > Data Model > Classes & Properties > Database class Mapping

Use the New External Database Table Class Mapping button (for externally mapped classes only) to create a new database table instance or edit an existing database table instance and properties that associate a class (and its derived classes) with an existing relational database table or view in the Pega database or an external database.

Another option is:

 -- Go to Records > SysAdmin > Database Table

 -- Select the class which you want to map to a different table.

 -- Select the Database and enter the Table name.

1.Using the structure of pc_work create a dedicated table 

2. Map the Database Table instance of the work class pointing to newly created table.

Please find the below link for more info https://community.pega.com/sites/default/files/help_v72/database/database2/databasetableswork.htm