Hello! I do ER-model, which was set in the university. This is how it is formulated:
High school. Human Resources Department. Units of the university. Staff list (planned distribution of rates and positions by departments). Employees. Appointments, relocations, dismissal of employees. Combining positions.
Expected requests:
- Find people who have worked in all divisions.
- Find units in which there are free bets on staffing.
- For all people show their current salaries.
- Find the lowest paid positions and divisions.
- For the specified employee to find the size of his salary in September 2009.
- Find those units that require staff reductions according to the staffing table, availability of employees of retirement age.
The model itself did, it looks like this: 
I can not figure out one thing: if a person gets a job at the same job twice. Now, with such a model it is possible ... How to ban it?
