select aidaentrance_namecrkslccksl fromselect from entrance_management aleft joinselect bentrance_idbentrance_namesumcase when blx=1 then bsl else 0 end rkslsumcase when blx=2 then bsl else 0 end cks

可以使用COALESCE函数将NULL替换为0，修改查询语句如下：

select a.id,a.entrance_name,COALESCE(c.rksl,0) as rksl,COALESCE(c.cksl,0) as cksl from (select * from entrance_management) a left join (select b.entrance_id,b.entrance_name,sum(case when b.lx=1 then b.sl else 0 end) rksl,sum(case when b.lx=2 then b.sl else 0 end) cksl FROM real_traffic_statistics b group by b.entrance_id,b.entrance_name) c on a.id = c.entrance_id