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17 lines
823 B
SQL
17 lines
823 B
SQL
SELECT MAX(price) as MAX_PRICE FROM Products; -- Get the most expensive product
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SELECT AVG(grade) as AVG_GRADE FROM Exams WHERE id = 0; -- Get the average grade for an exam
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-- Aggregation with grouping (Remember, only aggregates and cols in GROUP BY clause can
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-- appear in SELECT clause!)
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SELECT id, AVG(grade) as "Average Grade", COUNT(grade) as "Count"
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FROM ExamResults GROUP BY id; -- Average grade for each exam and number of students taking it
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SELECT id, AVG(grade) as avg, COUNT(grade) as cnt FROM ExamResults
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GROUP BY id HAVING cnt > 0 ORDER BY avg DESC LIMIT 20;
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-- Get exam details for all exams as filtered before
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SELECT * FROM (
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SELECT id, AVG(grade) as avg, COUNT(grade) as cnt FROM ExamResults
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GROUP BY id HAVING cnt > 0 ORDER BY avg DESC LIMIT 20
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) as filtered JOIN Exams e ON filtered.id = e.id;
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