Run dry report parameters to achieve linkage effect

I read a lot on the Internet, and they are implemented in a way like city==B2(province).toString(),

This method can be implemented, but it is slightly bloated. The following describes a relatively simple type of writing.

Preparation: Take the customer type driving the document type linkage as an example

The first step; in the parameter template, through configuration -> data set -> create a new customer type custType data set whose data set type is complex sql, as follows

Step 2: Create a new document type data set in the same way. Union is the data source of three customer types as follows:

Step 3: Right-click in the input input box of the certificate type - "Fill in Properties -" and perform the following settings in turn

Step 4: The last and most important step is to set the Web features as shown below, which can be achieved by c_custtype = ${c10}, isn't it very powerful!