Retrieving or deleting a specific row from a nested table

 Hi,There is a requirement where in i need to use nested tables concept.

that is table whose specific column will again hold multiple rows and columns data using object types and this would continue further.

In this scenario is there a way for us to retrieve a specific record or delete a specific record.

Will there be any difference in retrieving/deleting process if i use object type and table type.

If there is some example which can explain above scenario , it would be grateful.

Uday