[SQL] 기본 Aggregate Function

■ 코드카데미(codecademy) SQL 연습해보기

https://www.codecademy.com/courses/learn-sql/lessons/aggregate-functions/exercises/review

■ Cheating Sheets

https://www.codecademy.com/learn/learn-sql/modules/learn-sql-aggregate-functions/cheatsheet

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LESSON 3 : Aggregate Function

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COUNT()

SELECT COUNT(*)
FROM employees
WHERE experience <5;

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SUM()

SELECT SUM(salary)
FROm salary_disbursement;

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MAX() / MIN()

SELECT MAX(amount)
FROM transactions;

SELECT MIN(amount)
FROM transactions;

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AVG()

SELECT AVG(salary)
FROM employees
WHERE experience < 5;

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ROUND()

SELECT year,
    ROUND(AVG(rating),2)
FROM movies
WHERE year = 2015;

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GROUP BY

SELECT rating,
    COUNT(*)
FROM movies
GROUP BY rating;

SELECT COUNT(*) AS 'total_movies',
    rating
FROM movies
GROUP BY 2
ORDER BY 1;

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HAVING

SELECT year
    COUNT(*)
FROM movies
GROUP BY year
HAVING COUNT(*) > 5;