Append Query with unique duplicates

[milkman2500]

Hi,

I'm attempting to create an append query that will add new records only if there isn't an equivalent record already existing. Typically I would add the existing table to the query, and only add new records if the same do not exist. In this case, the table is maintaining records over time (start date and end date).

I have 4 tables:

[t_employees]
employee_ID
employee_name

[t_cities]
city_ID
citiy_name

[t_city_assignment]
city_assignment_ID
start_date
end_date
employee_ID
city_ID

[t_temp_employees]
effective_date
employee_ID
city_ID

I'm checking if [t_temp_employees].[effective_date] <> [t_city_assignment].[start_date]. However, if the employee has historical entries it will still add a record (in fact, it'll add multiple records).

How can I append a new record only if one for the same time period does not exist?

 

[milkman2500]

Problem solved! I updated the index to ensure unique records for multiple fields that include the dates.