Question

Using an ADODB connection object, I am able to use SQL DDL with MS Access (joy!). The odd thing is that sometimes declared foreign key references show up in Access’ Relationship View – this would be great for visualization, and to print off to show stakeholders – but sometimes it doesn’t. For example, I create an Employees table, and a Dep_Policy table with a foreign key reference to Employees (example from Ramakrishnan book). This shows in the relationship view. I now create two new tables using the same DDL, but change the names to Cat and Dog, as a test. Only Dog shows in the Relationship view, not Cat. Here’s the code:

Sub createTestSchema()

Dim cnn1 As ADODB.Connection
Dim cmd1 As ADODB.Command

Set cnn1 = CurrentProject.Connection
Set cmd1 = New ADODB.Command

Dim sqlArr As ArrayList
Set sqlArr = New ArrayList
sqlArr.Add ("CREATE TABLE Employees(ssn integer identity(0,1), name text(100), lot     text(50), primary key (ssn))")
sqlArr.Add ("CREATE TABLE Dep_Policy(pname text(20), age integer, cost currency, ssn integer, primary key (pname, ssn)," & _
            "FOREIGN KEY (ssn) references Employees(ssn) ON DELETE CASCADE)")
sqlArr.Add ("CREATE TABLE Cat(ssn integer identity(0,1), name text(100), lot text(50), primary key (ssn))")
sqlArr.Add ("CREATE TABLE Dog(pname text(20), age integer, cost currency, ssn integer, primary key (pname, ssn)," & _
            "FOREIGN KEY (ssn) references Cat(ssn) ON DELETE CASCADE)")
With cmd1
    .ActiveConnection = cnn1
    .CommandType = adCmdText
    Dim i As Integer
    For i = 0 To sqlArr.size - 1
        .CommandText = sqlArr.GetItem(i)
        .Execute
    Next
End With
End Sub

How do I ensure that the foreign key references show up in the Relationship view? For this test schema, most tables appear but in my actual schema few appear. Using MS Access is a client requirement. (btw ArrayList is a custom class)

Answer 1

In earlier versions, you’d right-click the workspace in the “Relationships” window, and select “Show all”.

Showing all tables and their relationships wasn’t (isn’t?) the default, because in a database that has 500 tables, the diagram would be mostly unreadable. In fact, in most databases, automatically showing all tables and relationships makes an unreadable diagram. It takes a fair bit of moving things around manually, and often selecting just closely related parts of a schema at a time, to make a readable diagram.