concat(

use SEMIN ;

SELECT

age, COUNT(*) as age_cnt

FROM

parent

GROUP BY

age ;

CREATE table test_comment(

_id int AUTO_INCREMENT COMMENT '기본키',

name int NOT NULL DEFAULT 0 COMMENT '이름',

age int NOT NULL DEFAULT 0 COMMENT '나이',

PRIMARY KEY(_id)

) ENGINE=INNODB ;

SELECT

distinct age

FROM

parent ;

SELECT

distinct age, _id