What do to if you want to create a site column that refers to external data?
As you can see in the image below i is not posible to create a site column of the type “external data”.
Dispite you can not create a site column of the type “external data” there is a workaround for getting a site column of this type.
First of al what you need to do is create a list of external data.
You can create this list by going to (or create) the external content type (in the SharePoint designer). In the following image you can see (in red) that it is posible to create a SharePoint list that refers to the external data.
In my case I created a list ExternalContacts. This is a testlist so don’t mind the content of the list. After creating the list you can check it by going to the list.
This list should look like this:
Now we are going to create the site column.
As you saw in the first image there is no type called “external data”. Instead of endlessly searching for this specific type we just will create a site column of the type “lookup”.
When you select this type, you can select the list with external data.
When we save the site column it will be created.
If we go and take a look at the site column you will see that the type of the site column isn’t “lookup” anymore but it is changed to “external data”.
Here it is proved that it is posible to create site columns with external data.
Dispite of the fact it is posible to create external data site columns with the workaround there are some disadvantages with the “external data”-site columns.
One of the disadvantages could already be seen in the creation of the “lookup”-site column.
When you create a “lookup”-site column that refers to values from a non-external data list it is posible specify that “multiple values” are allowed.
So SharePoint already knows while creating the site column if it refers to external or non-external data.
I hope this workaround will help you a lot further with your problems connecting to the external data.