Home Database Mysql Tutorial mysql-MySQL联接查询到的显示结果

mysql-MySQL联接查询到的显示结果

Jun 06, 2016 am 09:41 AM

mysqlselect联接查询数据库

表:fruits的字段f_id为primary key
图片说明
表:suppliers的字段s_id为primary key与fruits的s_id有相同的数据类型
图片说明
然后使用这2句查询语句:
1、select suppliers.s_id,s_name,f_name,f_price from suppliers inner join fruits on suppliers.s_id=fruits.s_id;
查询的都结果如下:
图片说明
2、select suppliers.s_id,s_name,f_name,f_price from fruits inner join suppliers on fruits.s_id=suppliers.s_id;
查询到的结果如下:
图片说明

可以确定的是查询的结果肯定是一样的,但是问题是使用第一句查询语句的条件是suppliers.s_id=fruit.s_id,我的理解是,当我们连接两张检索数据的时候,检索的方式是首先逐行扫描suppliers表中s_id的记录,只有条件suppliers.s_id=fruit.s_id匹配,结果才会被检索出来,所以首先要从表suppliers的s_id匹配表fruits的s_id的相等项,按道理说第一句查询语句查询到的结果应该是按照表suppliers的s_id顺序显示,为什么两个查询语句的显示结果的都是按照friuts本身的s_id的排列顺序?

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