Write a SQL query to rank employees by salary within each department.
| name | department | salary | dept_rank | |------|------------|--------|-----------| | Karthik Sundaram | Engineering | 95000 | 1 | | Ananya Singh | Engineering | 90000 | 2 | | Aarav Sharma | Engineering | 85000 | 3 | | ... | ... | ... | ... |