I have go through this but I couldn't understand. Can I join reation without primary key or partial key? If yes what is the answer for following question.

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1 Answer 1


Yes, you can join on any columns in a query. Primary and Foreign Keys are for Referential Integrity.

Select Item.IName, Item_Supply.AvailableQuantity
From Item
Join Item_Supply ON Item.ItemKey = Item_Supply.ItemKey
JOIN Supplier ON Item_Supply.SupplierKey = Supplier.SupplierKey
JOIN Country ON Supplier.NationKey = Country.CountryKey
JOIN Region ON Country.RegionKey = Region.RegionKey
Where Item_Supply.AvailableQuantity > 1000
AND Region.RName = 'East Asia'
  • Not sure what DBMS you are using, but I coded MSSQL
    – SS_DBA
    Commented Oct 10, 2016 at 17:09
  • I need relational algebra not a sql query
    – Blasanka
    Commented Oct 10, 2016 at 17:25
  • 2
    So you should be able to convert my select statement into your relational algebra. If you can post your answer after, I'd like to see the result.
    – SS_DBA
    Commented Oct 10, 2016 at 17:30

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