[MYSQL] MYSQL 집계함수

집계 함수

CREATE TABLE myRecode (
    recodeID int(10) unsigned auto_increment,
    memberID int(10) unsigned,
    javascript tinyint unsigned NOT NULL,
    html tinyint unsigned NOT NULL,
    css tinyint unsigned NOT NULL,
    myspl tinyint unsigned NOT NULL,
    react tinyint unsigned NOT NULL,
    PRIMARY KEY (recodeID)                                                                            
) charset=utf8;

INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(1, 80, 40, 10, 10, 90);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(2, 90, 20, 50, 80, 30);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(3, 30, 30, 80, 80, 40);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(4, 40, 90, 90, 70, 10);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(5, 10, 80, 50, 90, 30);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(6, 70, 70, 60, 80, 50);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(7, 50, 70, 40, 40, 60);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(8, 80, 60, 20, 60, 40);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(9, 90, 30, 60, 50, 30);
INSERT INTO myRecode(memberID, javascript, html, css, myspl, react) VALUES(10, 60, 10, 0, 30, 50);

집계함수의 종류

SELECT count(javascript) FROM myRecode;

SELECT sum(javascript) FROM myRecode;

SELECT avg(javascript) FROM myRecode;

SELECT max(javascript) FROM myRecode;

SELECT min(javascript) FROM myRecode;

그룹별 집계

GROUP BY

SELECT FROM 테이블명 GROUP BY 필드명;

SELECT memberID avg(javascript) FROM myRecode WHERE memberID IN(1,2,3,4,) GROUP