User`s guide

When using the Smart Linking feature to link tables using a field that is a component of multiple indexes
(two or more), Crystal Reports selects one of the indexes for the link. That index may or may not be
the one you want to use. Delete the link made by the Smart Linking feature and manually link the tables.
See Linking multiple tables for more information.
Note:
Not all DBMS applications support indexed tables. Verify that your database uses indexes before trying
to select an index for linking. Refer to your DBMS documentation to find out if your DBMS can use
indexes, and to learn how to create them.
23.5.9 Link processing order
When there is more than one link, Crystal Reports needs to know in what order it should process the
links. By default, the processing order matches the order in which the links appear on the Links tab.
Use the arrow buttons in the Links Order dialog box to change the default order.
For example, if you have chosen the Credit, Customer, Orders, and Orders Details tables from the
Xtreme sample database, the links tab shows the tables linked as follows.
In this case, the links will be processed first between the Credit/Customer tables, then between the
Customer/Orders tables, and finally between the Orders/Orders Details tables. The Links Order dialog
box shows you this default order and allows you to change the positions in the processing hierarchy
as you require.
Note:
Different link orders may result in different data sets returned for use in your report. As well, link order
has a significant effect on performance.
2012-03-14530
Understanding Databases