HP Intelligent Management Center Standard Software Platform - Manual (Page 677)

• Some DBMS applications allow you to convert the field value to another
data type in the index. For instance, the field in the table can be numeric,
while the index converts the field value to a string. However, if you choose
to use that field to link to another table, you must link to a field of the
original data type. You cannot link a string value to a numeric field that
has been converted to a string in the index.
• If you are linking tables from two different ODBC data sources, MS SQL
Server and Oracle, for example, you can only use string fields to link the
tables. String fields are stored in databases in the same manner,
regardless of the data source. Other types of values, however, may not
be stored the same way in different data sources, so you cannot link
different data sources in Crystal Reports using anything other than string
values.
• When linking direct-access database tables using native drivers
(non-SQL), the only join type available is Left Outer join.
Changing the index used in linking
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.
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.
Crystal Reports 2008 SP3 User's Guide 677
25 Understanding Databases
Linking tables