ACS Schema - Key issue

I created an Integer field and then assigned it as custom identification key. I haven't assigned Automatic primary key.

I also want Create, Duplicate and Delete permissions for this resource data. When i started "Prepare publication" process, I am getting the below mentioned error.

Please provide a fix for this

Error: "At least one key field in 'Client Id (clientId)' must have a default value to authorise creating data."

I am trying to achieve the below schema definition in Campaign standard.(Note: There is no default value assigned here) Is this possible?

Schema in Campaign Classic:

    <attribute label="Client Id" name="clientId" sqlname="CLIENT_ID" type="int64"/>

    <key internal="true" name="PK">

      <keyfield xpath="@clientId"/>

    </key>