1.left jon on 条件失效 ,原sql,会导致a的记录全部查出来,and 条件没有起作用
select a.id,a.name,b.address,c.math
from tablea a left join tableb b
on a.id = b.id
and a.name like "%mi%"
left join tablec c
on a.id = c.id
改进sql 在最后用where来进行处理,还有条件的话加and
select a.id,a.name,b.address,c.math
from tablea a left join tableb b
on a.id = b.id
left join tablec c
on a.id = c.id
where a.name like "%mi%"