You can see that the default value from the link Report Parameter is
automatically filtered down to our Data Set. Use of this method is preferred, as
it automatically creates that binding for you. It takes out the additional steps of
creating the Report Parameter separately from Data Set Parameters.
Dynamic Report Parameters and Filters
We have seen how we can work with database-driven data and Report Parameters
to filter data, using parameter binding between Report Parameters and Data Set
Parameters. You may ask yourself, why did we go through the first exercise when
the second exercise was so much easier? The reason is that this concept of binding
through expressions is used a lot in BIRT. We will explain this in more detail in
Chapter 12, when we discuss scripting. You may remember the Data component,
which displayed text from a Data Set. The way it does that is by binding the data to
the text element through an expression. In the next topic, we are going to see this
expression binding again.
Report Parameters can require manual input from a user; you can also have prepopulated
drop-down boxes for Report Parameters that are created at design time, or
even populated from a database or other Data Set. This is useful for cases where the
input needs to be exact; it is assumed that the user does not know all of the possible
values, or exactly what information they are looking for.
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