User`s guide

23.5.10 Linking options
Crystal Reports enables you to specify the type of join and type of link you want to use when linking
tables. You can also enforce the use of tables in your joins. Joins and links indicates how linked fields
in two tables are compared when records are read. Join, enforce, and link options can be specified in
the Link Options dialog box. Using the various join enforcement options can ensure that linked tables
are included in the SQL query, even when none of the fields in the table are used in the report.
Note:
When you link fields using joins, no indexed fields are required.
The join types are:
• Inner join
• Left Outer join
• Right Outer join
• Full Outer join
The enforce join options are:
• Not Enforced
• Enforced From
• Enforced To
• Enforced Both
The link types are:
• Equal [=] link
• Greater Than [>] link
• Greater Than Or Equal [>=] link
• Less Than [<] link
• Less Than Or Equal [<=] link
• Not Equal [!=] link
23.5.10.1 Inner join
An Inner join is the standard type of join. The result set from an Inner join includes all the records in
which the linked field value in both tables is an exact match. For instance, you can use an Inner join to
view all customers and the orders they have placed. You will not get a match for any customer who
has not placed orders.
2012-03-14531
Understanding Databases