25 lines
1.3 KiB
SQL
25 lines
1.3 KiB
SQL
-- List the top-10 of provinces for which the difference between the total number of items in purchases of the last 10 days and the preceding period of 10 days is the largest (i.e., the increase is large; we do not look for the largest decreases); list the full name of the province, the full name of the country, and the number of purchases in the last 10 days, as well as in the preceding period of 10 days; order the results by the size of the difference. Note that if there is no preceding period, the outcome is supposed to be empty.
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-- Expected Heading: RELATION {province CHARACTER, country CHARACTER, qty_last10 INTEGER, qty_1020 INTEGER}
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-- How do you treat the default case as showed in the instructions?
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SELECT province.name AS province, country.name AS country, qty_last10, (qty_last20-qty_last10) AS qty_1020
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FROM (
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SELECT province, SUM(qty) as qty_last10
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FROM Purchases
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WHERE time > date((SELECT MAX(time) FROM Purchases),'-10 days')
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GROUP BY province
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) AS L
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JOIN (
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SELECT province, SUM(qty) as qty_last20
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FROM Purchases
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WHERE time > date((SELECT MAX(time) FROM Purchases),'-20 days')
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GROUP BY province
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) AS P ON L.province = P.province
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JOIN province ON L.province = province.ROWID
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JOIN country ON province.country = country.code
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ORDER BY (2*qty_last10-qty_last20) DESC
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LIMIT 10
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;
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