Importing vs. Linking Database Files

You have the choice of importing or linking data from other databases, but how do you decide which type of access is best? Here are some guidelines.

You should consider importing another database file when any of the following is true.

• The file you need is relatively small and is not changed frequently by users of the other database application.

• You don’t need to share the data you create with users of the other database application.

• You’re replacing the old database application, and you no longer need the data in the old format.

• You need to load data (such as customers or products as we mentioned earlier) from another source to begin populating your Access tables.

• You need the best performance while working with the data from the other database (because Access performs best with a local copy of the data in Access’s native format).

On the other hand, you should consider linking another database file when any of the following is true.

• The file is larger than the maximum capacity of a local Access database (2 gigabytes).

• The file is changed frequently by users of the other database application.

• You must share the data on a network with users of the other database application.

• You’ll be distributing your application to several individual users, and you will need to make changes to the queries, forms, reports, and modules in the application without disturbing data already entered in the tables.

Inside Out-Using Linked Tables in a Complex Application Is a Good Idea 

Even when we’re building an application that we know will be run by only a single user, we usually create a separate .accdb file that contains all the tables and link those tables back into the .accdb file that contains all our queries, forms, reports, and code. If we’ve been careful creating our original table design, we rarely have to change it. But users are always thinking up some new feature that they would like to have. We can add a new form or report and send the user an update without having to disturb all the data they’ve already entered.

If you look closely at the tables in the Conrad Systems Contacts sample database (Contacts.accdb), you can see that most of the tables have a little arrow next to the table icon in the Navigation Pane, like this:

This indicates that these tables are linked from another data source.

Note 

The samples in this chapter use data you can find in files on the companion CD. You can import the data into or export the data from the Conrad Systems Contacts or Housing Reservations databases. You might want to work from a copy of these databases to follow along with the examples in this chapter. You can find the result of following many of these examples in the ImportLink.accdb sample database, which contains a Companies table that has columns using nearly every available data type in Access.