The strategy of pushing new products to current customers based on their past purchases. Cross-selling is designed to widen the customer's reliance on the company and decrease the likelihood of the customer switching to a competitor.
When deciding whether to add an extension column to a base table or to use columns in an extension table, consider the following recommendations:
* Add extension columns to base tables when the data you need to store almost always exists for a given base record and it is accessed regularly. By avoiding the join used with an extension table, this approach often results in better performance. However, note that it can result in slower access to the base table if there is a lot of data (that is, many large fields have been added and they are always populated), because fewer rows now fit on one page.
NOTE: When an extension column will be regularly specified in user queries, it is likely to need an index on the column that may need to include other base table columns; and therefore should be added to the base table.
* Use columns in an extension table when a one-to-many extension fields are required, and the view displaying this data is accessed infrequently. In this case, the join is executed for the extension table, but only when this view is accessed.
* As a general rule, if you plan to display additional attributes in a list applet, add extension columns to the base table; if you plan to display additional attributes in a form applet, use extension table columns.