hi Leo,

On 19.12.2009 07:58, Leo wrote:
Data entry could be though a form or directly from table, but there must be
a control or constrain over validity of date ranges (the span between
StartDate and EndDate) in a way that no two records overlaps each other for
the same employee and also no gap between entries.
If the constraint 'no gap' is a necessary, significant business rule
then the solution is quite simple:

Use no EndDate. Store only the employee's ID, the salary and the start
date. The end date is determined by either the next records start date,
or by an external date reflecting the employee's state - fired at.

mfG
-- stefan --