关联子查询的组函数改写
SELECT department_id, employee_id, salaryFROM EMPLOYEES e
WHERE 1 =
(SELECT COUNT(DISTINCT salary)
FROM EMPLOYEES
WHERE e.department_id = department_id
AND e.salary <= salary);
select a.department_id, e.employee_id , e.salary
from
(selectdepartment_id, max(salary)maxsal
from employees
group by department_id) a , employees e
where a.department_id =e.department_id
and a.maxsal=e.salary ;
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