SQL进阶--分析函数

分析函数提供一系列比较高级的SQL 功能。分析函数时建立在数据窗口（over 在一定的数据库范围进行数据分析），在一定的数据范围进行排序、汇总等。

1.查询当前员工所在部门的平均工资、最高工资和最低工资，即可通过分析函数来实现。

SELECT e.last_name,

e.salary,

d.department_name,

AVG(e.salary) over(PARTITION BY d.department_name) department_avg_salary,

MAX(e.salary) over(PARTITION BY d.department_name) department_max_salary,

MIN(e.salary) over(PARTITION BY d.department_name) department_min_salary

FROM employees e, departments d

WHERE 1 = 1

AND e.department_id = d.department_id;

分析函数续。。。

2.将一个部门内的员工的工资从高到低进行排序，注意三种排序结果是不一样的。

SELECT d.department_name,

e.last_name,

e.salary,

rank() over(PARTITION BY d.department_name ORDER BY e.salary DESC) dept_salary_rank1,

dense_rank() over(PARTITION BY d.department_name ORDER BY e.salary DESC) dept_salary_rank2,

row_number() over(PARTITION BY d.department_name ORDER BY e.salary DESC) dept_salary_rank3

FROM employees e, departments d

WHERE 1 = 1

AND e.department_id = d.department_id;