SELECT user_id,
nickname,
CONCAT_WS(' ', city, street_address1, street_address2) '전체주소',
CONCAT_WS('-', substr(tlno, 1,3), substr(tlno, 4,4), substr(tlno, 8,4)) '전화번호'
from USED_GOODS_USER u right join USED_GOODS_BOARD b on u.USER_ID=b.WRITER_ID
group by b.WRITER_ID
having count(BOARD_ID) >= 3
order by user_id desc주소, 전화번호 합치기
- concat: 잇기, Null 포함되면 null 반환
- concat_ws: 구분자로 잇기, null 반환 안함