User's Manual

Reps.
When a customer is reassigned to a new sales rep, the Customer table is
updated. The UPDATE is replicated as an INSERT or a or a DELETE to the
old and new sales representatives, respectively, so that the customer row is
properly transferred to the new sales representative.
☞ For information on the way in which Adaptive Server Anywhere and
SQL Remote work together to handle this situation, see “Who gets what?”
on page 86.
When a customer is reassigned, the Contact table is unaffected. There are
no changes to the Contact table, and consequently no entries in the
transaction log pertaining to the Contact table. In the absence of this
information, SQL Remote cannot reassign the rows of the Contact table
along with the Customer.
This failure will cause referential integrity problems: the Contact table at
the remote database of the old sales representative contains a cust_key value
for which there is no longer a Customer.
Use triggers to maintain
Contacts
The solution is to use a trigger containing a special form of UPDATE
statement, which does not make any change to the database tables, but which
does make an entry in the transaction log. This log entry contains the before
and after values of the subscription expression, and so is of the proper form
for the Message Agent to replicate the rows properly.
The trigger must be fired BEFORE operations on the row. In this way, the
BEFORE value can be evaluated and placed in the log. Also, the trigger
must be fired FOR EACH ROW rather than for each statement, and the
information provided by the trigger must be the new subscription expression.
The Message Agent can use this information to determine which subscribers
receive which rows.
Trigger definition The trigger definition is as follows:
CREATE TRIGGER UpdateCustomer
BEFORE UPDATE ON Customer
REFERENCING NEW AS NewRow
OLD as OldRow
FOR EACH ROW
BEGIN
// determine the new subscription expression
// for the Customer table
UPDATE Contact
PUBLICATION SalesRepData
OLD SUBSCRIBE BY ( OldRow.rep_key )
NEW SUBSCRIBE BY ( NewRow.rep_key )
WHERE cust_key = NewRow.cust_key;
END;
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