Crystal Reports supports several types of joins that can be used to link tables or views in a report. Here are the different types of joins available in Crystal Reports:

1. Inner Join : An inner join returns only the rows that have matching values in both tables being joined. It retrieves records where the joining condition is satisfied in both the primary and secondary tables. This type of join excludes unmatched records from both tables.

2. Left Outer Join : A left outer join returns all the rows from the primary (left) table and the matching rows from the secondary (right) table. If there is no match in the secondary table, null values are returned for the corresponding fields. Left outer joins are commonly used to retrieve all records from the primary table, even if there are no matches in the secondary table.

3. Right Outer Join : A right outer join returns all the rows from the secondary (right) table and the matching rows from the primary (left) table. If there is no match in the primary table, null values are returned for the corresponding fields. Right outer joins are less commonly used in Crystal Reports, as most databases support left outer joins and provide equivalent functionality. 4. Full Outer Join : A full outer join returns all the rows from both the primary and secondary tables. It includes all records from both tables, whether they have matching values or not. If there is no match, null values are returned for the fields from the non-matching table. Full outer joins are less common in Crystal Reports as they are not directly supported. However, they can be achieved through workarounds like using union queries.

5. Cross Join : A cross join, also known as a Cartesian join, returns the Cartesian product of the two tables being joined. It combines each row from the primary table with every row from the secondary table. Cross joins can result in a large number of records, so they should be used cautiously and with appropriate filtering conditions.

The choice of join type depends on the relationship between the tables and the desired result. Inner joins are commonly used when there is a one-to-one or one-to-many relationship between the tables. Left outer joins are useful when all records from the primary table should be included, even if there are no matches in the secondary table. Cross joins are typically used when you want to combine every row from one table with every row from another table.

Crystal Reports provides a graphical interface for creating and modifying joins, allowing users to define the join type and the joining condition between tables.