题解 | #平均工资#

SELECT AVG(salary) AS avg_salary
FROM salaries
WHERE salary NOT IN (
    SELECT MAX(salary) FROM salaries WHERE to_date = '9999-01-01'
) 
AND salary NOT IN (
    SELECT MIN(salary) FROM salaries WHERE to_date = '9999-01-01'
)
AND to_date = '9999-01-01';
 NOT IN 子句期望子查询返回单列的结果，需要为 MAX(salary) 和 MIN(salary) 分别编写两个独立的子查询。