I need to write a relational algebra query for the following:
Show the item_ID, item description and category description for all items
where the supplier uses "rail" as the delivery_method.
The relations (tables) and attributes are as follows:
Item (item_ID, description, category, price, qty_on_hand)
Category (code, description, tax_rate)
Supplied_by (item_ID, supplier, date, delivery_method)
notes:
1. "Item" and "Supplied_by" tables are linked by their primary keys.
2. The primary key for the "Category" table (code) is linked to the category
attribute of the "Item" table.
Any help with this would be highly appreciated.
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