Sybase DC38133-01-0902-01 manual That this subquery can be multi-valued, Can be multi-valued, 117

	Chapter 7. SQL Remote Design for Adaptive Server Anywhere
	that this subquery can be multi-valued.
Multiple-valued	The subquery in the BEFORE INSERT trigger is a UNION expression, and
subqueries	can be multi-valued:
	...
	SELECT rep_key
	FROM Policy
	WHERE cust_key = NewRow.cust_key
	UNION ALL
	SELECT NewRow.rep_key
	...
	♦ The second part of the UNION is the rep_key value for the new sales
	representative dealing with the customer, taken from the INSERT
	statement.
	♦ The first part of the UNION is the set of existing sales representatives
	dealing with the customer, taken from the Policy table.
	This illustrates the point that the result set of the subscription query must
	be all those sales representatives receiving the row, not just the new sales
	representatives.
	The subquery in the BEFORE DELETE trigger is multi-valued:
	...
	SELECT rep_key
	FROM Policy
	WHERE cust_key = OldRow.cust_key
	AND rep_key <> OldRow.rep_key
	...
	♦ The subquery takes rep_key values from the Policy table. The values
	include the primary key values of all those sales reps who deal with the
	customer being transferred (WHERE cust_key = OldRow.cust_key),
	with the exception of the one being deleted (AND rep_key <>
	OldRow.rep_key).
	This again emphasizes that the result set of the subscription query must
	be all those values matched by sales representatives receiving the row
	following the DELETE.
Notes	♦ Data in the Customer table is not identified with an individual subscriber
	(by a primary key value, for example) and is shared among more than one
	subscriber. This allows the possibility of the data being updated in more
	than one remote site between replication messages, which could lead to
	replication conflicts. You can address this issue either by permissions
	(allowing only certain users the right to update the Customer table, for
	example) or by adding RESOLVE UPDATE triggers to the database to
	handle the conflicts programmatically.

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