[홈페이지 제작] 홈페이지 댓글 만들기 2 - 쿼리문 연습

insert into reply_tb(comment,board_id,user_id,created_at) values ('댓글1',1,1,now());
insert into reply_tb(comment,board_id,user_id,created_at) values ('댓글2',4,1,now());
insert into reply_tb(comment,board_id,user_id,created_at) values ('댓글3',4,1,now());
insert into reply_tb(comment,board_id,user_id,created_at) values ('댓글4',4,2,now());

쿼리연습

select * from board_tb bt inner join reply_tb rt on bt.id = rt.board_id ;

아우터 조인(게시글 목록보기 - 댓글 카운트 보이기)

select bt.*,count(rt.id) from board_tb bt left outer join reply_tb rt on bt.id = rt.board_id group by bt.id,bt.title,bt.content,bt.user_id,bt.created_at;

아우터조인(게시글 목록보기-댓글도 함께 보이기)

select bt.id, bt.title, bt.content, bt.user_id, bt.created_at, ifnull(rt.id, 0) rid, rt.board_id, ifnull(rt.comment,'')   from board_tb bt left outer join reply_tb rt on bt.id = rt.board_id;