我有两个表，例如 Employee 和 Project 表:
Employee (id, dept, joining_date)
Project (emp_id, project)
Project 具有来自 Employee 表的外键。
我必须查询 project 和 dept 并按照 joining_date 的顺序返回 Employee。哪个查询在以下查询的大数据集上运行得更快？
select * from Employee where id in (select p.emp_id from Project p join Employee e on p.emp_id = e.id where p.project = 'project1' and e.dept = 'dept1') order by joining_date
select * from Employee where id in (select p.emp_id from Project p join Employee e on p.emp_id = e.id where p.project = 'project1' and e.dept = 'dept1') and dept = 'dept1' order by joining_date
或者有没有更好更简单的方法？
最佳答案
使用IN()表达式的外部查询没有任何作用，完全没有必要。这将产生您需要的输出:
select e.*
from Project p
inner join Employee e on p.emp_id = e.id
where p.project = 'project1' and e.dept = 'dept1'
order by joining_date
关于mysql - 使用 IN 时比较两个 SQL 查询，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/35787200/