Mysql 选择花费如此长的时间来完成

我选择此选项以向用户显示以下建议

首先它将从一个用户那里获得关注，然后它将检查用户是否没有关注这个用户。检查用户是否未阻止此建议，以及建议是否未阻止用户并显示它

select c.user, c.nome, p.foto, f.user, f.following from following f

left join cadastro c ON c.id=f.following
left join profile_picture p ON c.id=p.user

where f.user in (select following from following where user = 1) and following <> 1 and following not in (select following from following where user = 1)

and (c.id not in (select `block` from block where user = 1))
and (c.id not in (select `user` from block where block = 1))

group by following order by rand() limit 4

有什么改进的办法吗？大约需要3.4641秒

您的查询使用： 2个联接、4个嵌套查询、1个分组和1个排序。总成本应该很高

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尝试进一步简化查询。

您的查询有太多子查询要执行，请使用MySQL workbench实用程序检查您的查询执行计划。