Miniumum fields required in a form based on a query with two or more tables

[ITMA]

Are there any rules of thumb on how to avoid the "cannot update ... because
join key is not in the recordset" message? I gather it arises where there
are two tables in a query or form but one or more Key fields are missing
from the source query. Thinking about, for two tables with one join there
would be three fields with key field data - the primary field in the first
table, the related field in the second table and the primary field of the
second table. I have tried experimenting but have no as yet worked out the
inner workings of Access and what it truly needs and doesn't need in Queries
based on related tables.

 

[John Vinson]

Are there any rules of thumb on how to avoid the "cannot update ... because
join key is not in the recordset" message? I gather it arises where there
are two tables in a query or form but one or more Key fields are missing
from the source query. Thinking about, for two tables with one join there
would be three fields with key field data - the primary field in the first
table, the related field in the second table and the primary field of the
second table.

You usually don't need the primary key of the second table, but you do
need both the primary key of the 'one' table and the foreign key
(related) field.