php - update database entry and/or preserve exisisting entries -

i building php application checks birthdays of users in database. these users granted variety of gifts @ birthday, may pick one. keep track of picked, can see has claimed gift , still has gift waiting.

the target group of application companies, pay fee per employee part of application. application made make easier companies remember employees birthdays , show care.

as companies grow/shrink, hiring, firing employees, update employee list every month system able exclude no longer work there , add new employees.

now question is: how do smartest way?

if remove every employee associated given company, when given current employee roster, , insert new list scratch, loose association between employee , un/claimed gift in database.

on other hand, make sure preserve association in database, if add new employees , remove no longer on roster, how go smartest way?

the fields got on employees id, firstname, surname, email, birthday , company_id. neither of these way identify whether user in database (can argue email might work, if reason changed it, wouldn't work)

any suggestions more welcome.

the simplest answer add employee_id database. every company has internal ids use identify employees internally within system. necessary many purposes, including payroll, benefits, attendance, etc. therefore need add id field employee table , ensure roster receive contains these ids employees.

in addition, rather deleting entries employees no longer work company, can have flag indicating whether employment still active. add corresponding where clause queries.