mysqll的left join与right join的差异

left join和right join是MySQL中的两种不同的连接方式。

left join会选择左边的表作为驱动表，也就是左边的表是主导的，然后将右边的表与驱动表进行匹配，返回匹配成功的记录，如果右表中没有匹配的记录，返回NULL值。换句话说，left join会返回左表中的所有记录以及与之匹配的右表中的记录。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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