MySQL inner join 和 left join 的区别

看了网上一些讲的感觉还是云里雾里，不如自己实操一下。

sql语句，left join

select isad.type_id,
    isad.activity_id,
    isad.id,
    ist.type_name,
　　 f.status
    from
    inspection_store_activity_detail isad
    inner join inspection_store_type ist on isad.type_id = ist.id
    left join inspection_store_follow f on isad.id = f.activity_detail_id

　　

 

inner join 

select isad.type_id,
    isad.activity_id,
    isad.id,
    ist.type_name,
        f.status
    from
    inspection_store_activity_detail isad
    inner join inspection_store_type ist on isad.type_id = ist.id
    inner join inspection_store_follow f on isad.id = f.activity_detail_id

 如图，inner join在连接的表在要查询的字段有空时，该条记录不会被查询出来，主表信息也不保留。

left join 是主表信息都保留，连接的表有该字段展示，没有就展示null。