Say I have 2 tables，A and B，eachaentitycanpossiblyhavemultiplebentities，inonecaseifiwanttogetallb ' sofsomecertaina ' s，iging
select A.id aid，B.id bid from A
left join B on B.aid=A.id
where A.id=1
and it will return a result set like
aid bid
1 1
1 2
1 3
As you can see for the first column，all those1' sarekindaduplicates.isitpossibletomodifythesqlstatementtolethimreturnaresultltltike
aid bid
1，2，3
inotherwordstolinkallthebid ' stogetherasoneentity？
Also what if there's another table C，and each A can have multiple C's，howtoimakethesqlreturnaresultsetlike
aid bid cid
一，二，三十一，二
instead of
aid bid cid
1 1 1
1 2 1
1 3 1
1 1 2
1 2 2
1 3 2
Thank you very much
解决方案
What DBMS are you using？
I can't speak for others，but in MySQL，starting from 4.1，you can use GROUP_CONCAT
EG:
select A.id aid，group_concat(distinctb.id ) bid from A
left join B on B.aid=A.id
where A.id=1
GROUP BY a.id