Sybase DC38133-01-0902-01 manual Tuning extraction performance

	Chapter 8. SQL Remote Design for Adaptive Server Enterprise
	inserted; these rows being identified by the subquery
	SELECT contact_key
	FROM inserted
An UPDATE trigger for	The trigger for an UPDATE on the Contact table checks to see if the
the Contact table	cust_key column is changed, and if it has updates the subscription_list
	column.
	CREATE TRIGGER update_contact_sub_list
	ON Contact
	FOR UPDATE
	AS
	IF UPDATE ( cust_key )
	BEGIN
	UPDATE Contact
	SET subscription_list = Customer.rep_key
	FROM Contact, Customer
	WHERE Contact.cust_key=Customer.cust_key
	END
	The trigger is written using a join; a subquery could also have been used.
An UPDATE trigger for	The following trigger handles UPDATES of customers, transferring them to
the Customer table	a new Sales Rep:
	CREATE TRIGGER transfer_contact_with_customer
	ON Customer
	FOR UPDATE
	AS
	IF UPDATE ( rep_key )
	BEGIN
	UPDATE Contact
	SET Contact.subscription_list = (
	SELECT rep_key
	FROM Customer
	WHERE Contact.cust_key = Customer.cust_key )
	WHERE Contact.contact_key IN (
	SELECT cust_key
	FROM inserted
	)
	END

Tuning extraction performance

When extracting or synchronizing a user, the subscription-listcolumn can cause performance problems as it necessitates a full table scan.

If you are extracting databases for many users, and performance is a problem for you, you can use a subscription view to improve performance. The view must contain a subquery, which is used for extraction and synchronization only, and is ignored during log scanning. The tables involved still need to

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