220111 mysql

mysql

• DISTINCT: 범주 조회 (중복된 것을 제거하고 보여줌)

SELECT COUNT(DISTINCT author_fname) FROM books;

• LIKE: 단어가 포함된 검색조회

SELECT title FROM books WHERE title LIKE '%the%';

• GROUP BY: 그룹지어서 값을 구하고 싶을때

SELECT author_lname, COUNT(*) FROM books GROUP BY author_lname;

SELECT released_year, COUNT(*) FROM books GROUP BY released_year;

• Min, Max: 최소, 최대값 구할때

SELECT MIN(released_year) FROM books;
SELECT MAX(pages) FROM books;

SUB쿼리

SELECT * FROM books 
WHERE pages = (SELECT Min(pages) 
                FROM books); 

가장 적은 페이지를 가진 책의 이름과 페이지 가져오기

SELECT title, pages FROM books 
ORDER BY pages ASC LIMIT 1;

SUM: 합 구할때

SELECT SUM(pages) FROM books;

AVG: 평균 구할때

SELECT AVG(pages) FROM books;