Changes between Version 5 and Version 6 of querries

Timestamp:

09/24/25 15:53:54 (13 days ago)

Author:

221046

Comment:

--

querries

@@ -32 +32 @@
 ||'''Фактури по корисник по датум'''||[[Image(invoice_per_customer_after_date.png, width=700)]]|| Враќа сите фактури за избраниот корисник; ако е зададен датум, ги филтрира по тој датум и пресметува вкупната сума. ||
 
+-- Релациона алгебра за прашалникот: Најпопуларен артист по жанр за корисник --
+
+π g . genre_id, g . name → genre_name, ar . name → artist_name, COUNT (*) → play_count
+  γ genre_id, name, name, COUNT (*)
+   σ c . customer_id = 123
+    (ρ c customer ⋈ c . customer_id = i . customer_id
+     ρ i invoice ⋈ i . invoice_id = il . invoice_id
+      ρ il invoice_line ⋈ il . track_id = tr . track_id
+       ρ tr track ⋈ tr . genre_id = g . genre_id
+        ρ g genre ⋈ tr . album_id = a . album_id
+         ρ a album ⋈ a . artist_id = ar . artist_id
+          ρ ar artist) in let maxplaycounts =
+           π genre_id, MAX (play_count) → max_count
+            γ genre_id, MAX (play_count) playcounts in
+             π pc . genre_name, pc . artist_name, pc . play_count
+              (ρ pc playcounts ⋈ pc . genre_id = mpc . genre_id AND pc . play_count = mpc . max_count
+               ρ mpc maxplaycounts)
+
+
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