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Asked: 2026-05-28T15:42:26+00:00

Getting through some practice exam papers but in regards to the relational algebra I’m

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Getting through some practice exam papers but in regards to the relational algebra I’m confused as to how the infinity symbol (∞) works in this example:

π(pname(σ sid=123(Catalogue) ∞ Parts)

Where pname is from the Parts entity and sid is from the Catalogue entity. Now, I believe this is selecting the pname from Parts where the sid in Catalogue = 123.

Assuming I’m right, what the hell does ∞ mean here? It’s not a join, is it? If I was to write the query version, would I have to use a join?

Thanks

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1 Answer

  1. Editorial Team

    It doesn’t. There is no such symbol in relational algebra.

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