擅长:python、mysql、java
<p>我会猜出列名(因为你没有清楚地提到它们)。正确的外部联接是这样写的:</p>
<pre><code>select
i.chip_id as cat_id,
d.diet_req as diet,
r.req_name as req,
m.med_his as med
from catinfo i
left join catdiet d on d.chip_id = i.id
left join catmedical m on m.chip_id = i.id
left join catreq r on r.chip_id = i.id
</code></pre>
<p>根据需要更改列名</p>