Hi Akhil,
The content you say are the table data, right?
Normally when export we choose binary and when importing it's very quick as we aren't not merging but just importing the snapshop from the binary over the existing content.
I guest you want to "merge" data and as far as I know import is not the option for it.
These schemas are on same instance?
You can do insert B from select A where not exist on B (if don't want to overwrite). If you need to update you can do a step before deleting the content B where exists on A and will be overwriten and just insert B from select A.
Of course make an export of B before start these actions to be safe, as SHappens.
To prepare the SQL's you can build a script reading the view TABLE_COLUMNS
Regards, Fernando Da Rós