In *typical* use there would be 1 SQL statement for the core, and then one SQL statement per extension.

There are occasions that you would break this though.

If I were setting up an IPT on MySQL I would use views in the database, and manage those with the database database schema itself.  So something along the lines of:

  CREATE VIEW view_ipt_occurrence 

  AS SELECT id AS id, id AS occurrenceID, name AS scientificName … FROM specimen; 

  CREATE VIEW view_ipt_image AS SELECT s.id AS id, s.id AS 

  SELECT occurrenceID, i.image AS imageURL … FROM image i JOIN specimen s ON i.specimen_id=s.id; 

Then in the IPT on the occurrence mapping I would simply use this knowing it will auto map since the views use DwC terms as column aliases:

  SELECT * FROM view_ipt_occurrence;

  SELECT * FROM view_ipt_image;

Does that help at all?  

If you send your DB schema, we will be happy to help out with SQL mappings.

Thanks,

Tim