A cascading input control is one whose values depend on the selection made in a previous input control. You create a cascading input control using parameters in the query string of a related input control. In other words, the parameter you defined for an input control can be used in another query-based input control.

In a query-based example of cities and states such as:

Los Angeles | CA
San Francisco | CA
Denver | CO

the query may still generate a list of hundreds of cities to scroll through. Even though each city is easy to identify with the state, scrolling through a long list is time consuming. With cascading input controls, this example can have two input controls, one for the state and one for the city: The city input control is empty until the user selects a state.

For an especially large number of cities, you can use more cascading input controls, such as region of state, to reduce the list.

The parameter values determined by each cascading input control may or may not be used in the report. For example, if the report only shows data about a city, the country input control exists only to speed up the choice of city. However, if the report also shows information such as city average compared to country average for a given measure, the country parameter is also used in the report.

Parameters in Input Control Queries

Parameter substitution in query input controls follows the same approach as for JasperReports queries. Queries of all types of data sources can use parameter substitution, and $P, $P! and $X (for SQL queries) parameters are supported. The $X notation has two principal forms explained in the following list:

The value of the parameter is substituted into the query. In cases where the parameter contains a string, the substitution inserts the proper escape characters to create valid SQL. Use this for single-select input controls and simple comparison operators such as greater-than or less-than. For example:

select name from EMPLOYEES where deals_closed > $P{DEALS}

Do not use $P{parameter_name} with equality because the parameter value can be null, and field = NULL is not valid SQL. Instead use $X{EQUALS, ...} as explained below.

The value of the parameter is treated as raw text. The server replaces the parameter with the value of the input control without performing extra checking or value escaping. This is used in complex cases where the input control provides a piece of the query or sometimes the entire query.

This syntax performs equality verification and handles the case when the parameter value is null. Use this everywhere instead of the old column = $P{parameter_name} syntax. The $X{EQUALS...} syntax performs the following substitution before submitting the query:

column = parameter_value -- when parameter_value is non-null

column IS NULL -- when parameter_value is NULL

Use this parameter for cascading with multiple-select input controls. The $X{IN...} operator is true when the field value matches any one of the multiple values of the input control. In the country/cities example, we can allow the user to pick any number of countries, and show all the cities in the selected countries. The query-based input control would have the following query:

select city from ACCOUNTS where $X{IN, country, COUNTRIES}

If the user selects the values Canada, Mexico, and USA in the COUNTRIES multi-select input control, the $X{} syntax translates into the following query for the CITIES input control:

select city from ACCOUNTS where country IN ('USA','Canada','Mexico')

The $X syntax also supports the following operators. They are all designed to handle null input by generating 0 = 0 when the parameter value is null:

For more information on using $P, $P! and $X to build dynamic queries, see the TIBCO JasperReports Library Ultimate Guide and the TIBCO Jaspersoft Studio User Guide.

Any number of parameters can be used in a query, just as any number of input controls can be defined in a JasperReport. In addition to the standard input control parameters, a cascading input control query can use the built-in parameters described in Built-in Parameters for Query-based Input Controls.

Creating a Cascading Input Control

In this example, we'll create a cascading input control to allow users to report on orders for a specific city by selecting a country and then a city within that country. Our example uses Jaspersoft Studio to edit a JasperReport on the server. The report uses sample data from the SugarCRM database shipped with JasperReports Server.

We'll start with a report containing the following dataset fields: ORDERED, CUSTOMERID, EMPLOYEEID, SHIPCITY, and SHIPCOUNTRY.

Our sample report is based on the following query that requires the user to enter a city:

select * from orders where SHIPCITY=$P{City}

Creating the Country input control:

select distinct SHIPCOUNTRY from orders order by SHIPCOUNTRY

Creating the City input control:

Select distinct SHIPCITY from orders where SHIPCOUNTRY = $P{Country} order by SHIPCITY

Now when you run your report in JasperReports Server, You'll see an input control for country and another for city. After you select the country, the values available for city are those within that country. Notice that the Country value is not passed to the report. It is used only to help the user select a city.