Can we create multicolumn unique indexes on MS access databases?

Question

We'd like to prevent record duplication in our MS access database using a multicolumn unique index. Because of how the data is sent (via network), duplicate data is sometimes received. The data source does not send a unique ID, so the simplest option is to prevent duplicate records being inserted.

According to Unique Index Design Guidelines:

With multicolumn unique indexes, the index guarantees that each combination of values in the index key is unique. For example, if a unique index is created on a combination of LastName, FirstName, and MiddleName columns, no two rows in the table could have the same combination of values for these columns.

This is for SQL 2005 however, so I'm not sure it's possible using MS access.

I guess an alternative is to perhaps use the query (pseudo code):

insert into foobar (a, b, c) values ('x', 'y', 'z')
where (a <> 'x') and (b <> 'y') and (c <> 'z')

... but I feel like an index would be better.

Answer 1

Open the table in design view in MS Access, select the three columns that you want to make into the unique index, and then click the little key on the toolbar. You cannot have null values in a primary key (set).

Answer 2

Turns out you can create a multi-column unique index on an MS access database, but it's a little crazy if you want to do this via the GUI. There's also a limitation; you can only use 10 columns per index.

Anyway, here's how you create a multi-column unique index on an MS access database.

1. Open the table in design mode, and Design, select Indexes.
2. Create a new row and enter a value in the Index Name cell,
3. Choose the first column from the drop down menu.
4. Add a new row and leave the Index Name cell blank.
5. Choose the second column, and so on.

Here's what it should look like: