擅长:python、mysql、java
<p>假设您需要在计数前将3个表的信息汇总在一起,这样会更快:</p>
<pre><code>SELECT userid, SUM(ct) AS total
FROM (
( SELECT userid, COUNT(*) AS ct FROM trans1 GROUP BY userid )
UNION ALL
( SELECT userid, COUNT(*) AS ct FROM trans2 GROUP BY userid )
UNION ALL
( SELECT userid, COUNT(*) AS ct FROM trans3 GROUP BY userid )
)
GROUP BY userid
HAVING total >= 2
</code></pre>
<p>建议您在mysql命令行工具中进行测试,然后找出如何将其转换为python3 | Flask | Sqlalchemy</p>
<p>关于“隐藏数据库”的包,有趣的是,如果您要做任何不重要的事情,您仍然需要了解数据库是如何工作的。在</p>