Changes between Version 8 and Version 9 of querries


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Timestamp:
09/24/25 16:05:54 (13 days ago)
Author:
221046
Comment:

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  • querries

    v8 v9  
    3434= Релациона алгебра за прашалникот: Најпопуларен артист по жанр за корисник =
    3535
    36 PlayCounts=γ g.genre_id,g.name→genre_name,ar.name→artist_name,COUNT(∗)→play_count(σ c.customer_id=123((customer⋈invoice)⋈(invoice_line⋈track)⋈(track⋈genre)⋈(track⋈album)⋈(album⋈artist)))
     36!PlayCounts=γ g.genre_id,g.name→genre_name,ar.name→artist_name,COUNT(∗)→play_count(σ c.customer_id=123((customer⋈invoice)⋈(invoice_line⋈track)⋈(track⋈genre)⋈(track⋈album)⋈(album⋈artist)))
     37
     38!MaxPlayCounts=γgenre_id,MAX(play_count)→max_count​(!PlayCounts)
     39
     40Final_Result=π pc.genre_name,pc.artist_name,pc.play_count(PlayCounts⋈pc.genre_id=mpc.genre_id∧pc.play_count=mpc.max_count !MaxPlayCounts)
    3741
    3842** ← [wiki: Назад на почетна] **