統計某一類別最受歡迎的商品

WITH Produce AS(SELECT 'kale' as item, 23 as purchases, 'vegetable' as categoryUNION ALL SELECT 'orange', 2, 'fruit'UNION ALL SELECT 'cabbage', 9, 'vegetable'UNION ALL SELECT 'apple', 8, 'fruit'UNION ALL SELECT 'leek', 2, 'vegetable'UNION ALL SELECT 'lettuce', 10, 'vegetable') SELECT item, purchases, category, LAST_VALUE(item)OVER (PARTITION BY categoryORDER BY purchasesROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS most_popular FROM Produce

• fruit
• (orange, apple) = apple is most popular
• (orange, apple) = apple is most popular
• vegetable
• (leek, cabbage, lettuce, kale) = leek is most popular
• (leek, cabbage, lettuce, kale) = lettuce is most popular
• (leek, cabbage, lettuce, kale) = kale is most popular
• (leek, cabbage, lettuce, kale) = kale is most popular
  
  統計某一類別窗口內最受歡迎的商品，本窗口長度是四【前一，本身，后一，后２】

WITH Produce AS(SELECT 'kale' as item, 23 as purchases, 'vegetable' as categoryUNION ALL SELECT 'orange', 2, 'fruit'UNION ALL SELECT 'cabbage', 9, 'vegetable'UNION ALL SELECT 'apple', 8, 'fruit'UNION ALL SELECT 'leek', 2, 'vegetable'UNION ALL SELECT 'lettuce', 10, 'vegetable') SELECT item, purchases, category, LAST_VALUE(item)OVER (PARTITION BY categoryORDER BY purchasesROWS BETWEEN 1 PRECEDING AND 2 FOLLOWING) AS most_popular FROM Produce

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總結

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