1.使用以下语句:
SELECT MAX(salary),MIN(salary),AVG(salary),SUM(salary)
FROM employees
结果如下:
2.使用以下语句:
SELECT DATEDIFF(MAX(hiredate),MIN(hiredate)) DIFFRENCE
FROM employees
结果如下:
3.使用以下语句:
SELECT COUNT(*)
FROM employees
WHERE department_id=90
结果如下: