Question

So take the following example:

Sub CreateRelation()

   Dim db As Database
   Dim rel As Relation
   Dim fld As Field

   Set db = CurrentDb
   Set rel = db.CreateRelation("OrderID", "Orders", "Products")

   'referential integrity
   rel.Attributes = dbRelationUpdateCascade

   'specify the key in the referenced table
   Set fld = rel.CreateField("OrderID")

   fld.ForeignName = "OrderID"

   rel.Fields.Append fld

   db.Relations.Append rel

End Sub

I keep getting the error:

No unique index found for the referenced field of the primary table.

If I include the vba before this sub to create in index on the field, it gives me the error:

Index already exists.

So I am trying to figure this out. If there are not any primary keys set, will that cause this to not work? I am confused by this, but I really really want to figure this out. So orderID is a FOREIGN KEY in the Products Table

Answer 1

You can create a relationship manually through the interface, then reverse engineer it. Here is an Immediate Window session where I examined an existing relationship:

? currentdb.Relations.Count
 1 

? currentdb.Relations(0).Name
parentchild

? currentdb.Relations(0).Table
tblParent

? currentdb.Relations(0).ForeignTable
tblChild

? currentdb.Relations(0).Fields.Count
 1 

? currentdb.Relations(0).Fields(0).Name
id

? currentdb.Relations(0).Fields(0).ForeignName
parent_id

For reference, this is the sub used to create that relationship:

Public Sub CreateRelationship()
Dim strSql As String
strSql = "ALTER TABLE tblChild" & vbNewLine & _
    "ADD CONSTRAINT parentchild" & vbNewLine & _
    "FOREIGN KEY (parent_id) REFERENCES tblParent (id);"
CurrentProject.Connection.Execute strSql
End Sub

Don’t bother with the dbRelationUpdateCascade attribute until after you confirm you have sorted out which are the foreign table and key.