Joiner transformation is used for vertical consolidation. e.g
order-tbl
order-id, item-id, item-qty
item-tbl
item-id, item-price, item-desc
Using a join condition on order-tbl.item-id = item-tbl.item-id
you could print a report like this
order-id, item-id, item-price, item-desc
For vertical consolidation, I can't think of a scenerio needing other conditions like !=, >=, <=.
With lookup transformation, some core ETL tasks are made easy like
- Identifying if the incoming record is a new record (primary key doesn't exist) or an update to the existing record;
- Lookup a value e.g. lookup item-price from item-tbl to calculate order total