MySQL读取数据库结果排序时按特定的条件优先排序

商品表 tb_goods
帖子表 tb_posts
关联表 tb_relation

select * from tb_relation r
left join tb_posts p on p.id = r.postid
left join tb_goods g on g.id = r.goodsid
where r.goodsid = 100
order by p.id

selec * from table_name order by case when 字段名 = '2'  then 0 else 1 end

select * from tb_relation r
left join tb_posts p on p.id = r.postid
left join tb_goods g on g.id = r.goodsid
where r.goodsid = 100
order by case when (p.istop=1 or p.isboardtop=1) then 0 else 1 end