select a.*,b.num as 回帖数 from board a left join (select id,count(*) as num from reboard group by id) b on a.id=b.id
假设BOARD的主键为ID,REBOARD的外键为BOARDID SELECT BOARD.ID,ISNULL(T2.COU,0) FROM BOARD LEFT JOIN ( SELECT BOARDID,COUNT(1) 'COU' FROM REBOARD GROUP BY ID ) T2 ON BOARD.ID=T2.BOARDID
select *,(select count(1) from ReBoard where Board.贴id=ReBoard.贴id) 回贴数 from Board
from board a
left join (select id,count(*) as num from reboard group by id) b on a.id=b.id
SELECT BOARD.ID,ISNULL(T2.COU,0)
FROM BOARD
LEFT JOIN (
SELECT BOARDID,COUNT(1) 'COU' FROM REBOARD
GROUP BY ID
) T2 ON BOARD.ID=T2.BOARDID
from Board