Mysql 在我所看到的每种情况下，即使查询为In操作返回一组不变的行，也会为主查询的每个结果运行子查询。 select tasks.* from tasks where some criteria and task.project_id not in (s

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在我所看到的每种情况下，即使查询为In操作返回一组不变的行，也会为主查询的每个结果运行子查询。

select tasks.*
from tasks
where 
  some criteria
  and task.project_id not in (select id from project where project.is_template = 1);

select tasks.*
from tasks, project
where
  some criteria
  and task.project_id = project.id and project.is_template <> 1;

EXPLAIN select tasks.*
from tasks
where 
  some criteria
  and task.project_id not in (select id from project where project.is_template = 1);

EXPLAIN select tasks.*
from tasks, project
where
  some criteria
  and task.project_id = project.id and project.is_template <> 1;

select tasks.*
from tasks
where 
  some criteria
  and task.project_id in (select id from project where project.is_template <> 1);