add window function

.pre-commit-config.yaml

 repos:
   - repo: git@codechina.csdn.net:csdn/skill_tree_hook.git
-    rev: 15a330214a4d7c2e0c0e42b5dfc3121a56f4dc23
+    rev: 9430721405a57a809c0d93170fe307a89d979a4b
     hooks:
       - id: pre-commit
         verbose: true
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data/3.PostgreSQL高阶/3.SQL高级技巧/2.Window Function/salary.md

+# 工资最高的人
+
+现有员工信息表如下：
+
+```postgresql
+create table employee
+(
+    id     serial primary key,
+    name   text,
+    dept   text,
+    salary money
+);
+```
+
+下面哪条查询，可以给出每个部门工资最高的前五个员工的 id, name, dept, salary 四项信息？
+
+## 答案
+
+```postgresql
+select id, name, dept, salary
+from (select id, name, dept, salary, rank() over (partition by dept order by salary desc) as r
+      from employee) as t
+where r <= 5;
+```
+
+## 选项
+
+### 结构错误
+
+```postgresql
+select id, name, dept, max(salary) as salary
+from employee
+group by dept
+having id < 6;
+```
+
+### 结构错误
+
+```postgresql
+select l.id, l.name, l.dept, l.salary
+from employee as l
+         join (select max(salary) as salary, dept
+               from employee
+               group by dept) as r
+              on l.dept = r.dept and l.salary = r.salary
+where count(r.id) <= 5;
+```
+
+### 结构错误
+
+```postgresql
+select l.id, l.name, l.dept, l.salary
+from employee as l
+         join (select max(salary, 5) as salary, dept
+               from employee
+               group by dept) as r
+              on l.dept = r.dept and l.salary = r.salary
+```
+
+### 结构错误
+
+```postgresql
+select id, name, dept, salary, rank() over (partition by dept order by salary desc) as r
+from employee
+where r <= 5;
+```
+