Sybase DC38133-01-0902-01 manual To create a subscription view, 163

Chapter 8. SQL Remote Design for Adaptive Server Enterprise

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 have triggers defined to maintain the subscription-listcolumn.

❖To create a subscription view

1.Design a query that uses a subquery to select the proper rows for a subscription from a table.

For example, continuing the example from the preceding sections, the following query selects the rows of the Contact table for a user subscribed by rep_key value rep5:

SELECT *

FROM Contact

WHERE ’rep5’ = (SELECT rep_key

FROM Customer

WHERE cust_key = Contact.cust_key )

2. Create a view that contains this subquery. For example:

CREATE VIEW Customer_sub_view AS SELECT *

FROM dbo.Customer

WHERE ’repxx’ IN ( SELECT rep_key FROM dbo.Policy

WHERE dbo.Policy.cust_key = dbo.Customer.cust_key )

In this view definition, it does not matter what value you use on the left-hand side of the WHERE clause (repxx in the example above). The replication tools use the subquery for extraction and synchronization only. Rows for which the SUBSCRIBE BY value is in the subquery result set are extracted or synchronized.

3.Give the name of the view as a parameter to sp_add_article or sp_modify_article:

exec sp_add_article SalesRepData, ’Customer’, NULL, ’subscription_list’, ’Customer_sub_view’

The subscription_list column is used for log scanning and the subquery is used for extraction and synchronization.

☞For more information, see “Tuning extraction performance” on page 155, “sp_add_article procedure” on page 381 , and “sp_modify_article procedure” on page 398 .

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