Honestly, I personally did not encounter tasks when I need to export at the same time for an example of five tables and for each of them I need to apply a
But your question make sanse.
Of course, you can go the simplest way but the least attractive for users by adding one
where clause input field to the application. That will work by condition if the table is selected alone, then this field is available, if there is a lot of that is not available.
But the idea of processing multiple tables is more attractive
Therefore, I would do the following:
Near the All Data tables checkbox, I would add another called Use Where Clause
Further, the user turned on this checkbox and selected the required tables and then when he click on Export button (In this case, the text is better to change to something like Continue) the app will show to him popup includes the list with table name and near input for where clause.
There is an important point here. The application must keep the state of the filled fields until the final request is sent to the server to perform the export. Because there can be a lot of fields filled in and that if the user chooses an extra table or, on the contrary, he forgot to choose one of the tables. He will get a very bad experience if he has to fill it all over again.