Nick Grattan’s SharePoint Blog

When creating columns in lists or document libraries you can easily create a column that links to a column in another list using the “Lookup (Information already on this site)” column type:

You will notice that only lists in the current site are shown. What if you want to create a link to a list in another site in the site collection? You can do this using site columns – note though, this the technique described here only allows you to link to sites up the site hierarchy, and not in sub-sites.

To do this:

1. Navigate to the site which contains the list you want to link to.
2. Select the Site Actions + Site Settings menu command.
3. Click the Site Columns link under “Galleries”.
4. Click Create to create the site column.
5. Use the “Lookup (Information already on this site)” column type and select the list from “Get Information from” and the column from this list to display.
6. Now navigate to the list in the other site that needs to link to this list. Select Settings + List Settings.
7. Select the Add from existing site columns. You will find the column you created in (4) listed, and when selected, will contain the link to the list in the other site.

Thanks to Yann Faure for pointing this out to me.