That depends on the type of relationship field. A relationship field that only allows 1 selections is stored as the post ID of that selection and then you would query for posts there the value “=” that post ID. A relationship field that allows multiple values is stored as a serialized array and requires the “” around the post ID.
More question:
Are you using guberbug blocks? Is the relationship field a block?
If not the above, is the relationship field a sub field of another field; repeater, group, flexible content?
