Appending to the Access DB from c#

Question

I have c# app which should append rows to MS Access table.
That table is basically a composition of 3 tables (let's say they all have a single column
Table1 with column A, Table2 - column B, Table3 - column C
Query - INSERT INTO Table4 (SELECT A, B, C FROM Table1, Table2, Table3)
Obviously it runs ok only for first time only and generates "Duplicate records" error after that.
It's easy to handle within Access but not from c# code.
What do I do, so it only appends a new rows and ignores duplicates without writing a long code?

Elmar · Answer

I guess I shold explain the whole project - 3 tables are just like libriries: ID and Description; table 4 is a combination of ID1 ID2 ID3 and more fields for the combination. Want a real world example? Let's say Cities: CityID Name Commodities: CommodityID Title ProcessSteps: StepID Description I need to have a table with StepDurationInDays and AssignedPerson for each combination of City+Commodity+Step

Mahesh Chand · Answer

I think your question is not clear. Why do you have Table 4? What is in Table 4 if you already have separate 3 other tables. You may want to check the relationships between Tablet 4 and other tables and also check the constraints.