Number of Raises

Count how many times each employee's salary increased from one period to the next. Order by name.

Table schema

SalaryHistory(emp VARCHAR(10), salary INT, start_date DATE, end_date DATE)

Sample data

emp | salary | start_date | end_date
Ann | 50000 | 2024-01-01 | 2025-01-01
Ann | 60000 | 2025-01-01 | 2026-01-01
Ann | 75000 | 2026-01-01 | NULL
Bob | 40000 | 2024-06-01 | 2025-06-01
Bob | 42000 | 2025-06-01 | NULL