Before you start, you must understand the reporting
problem that you are trying to solve and what data is available to
solve it.
If you cannot address the following questions,
talk to your users about their reporting requirements:
- Do you and your users agree on the reporting requirements?
Issues to resolve can include multilingualism, performance,
security, and how to organize and combine query items and filters.
- Does the data source contain the data and metadata that
you need?
Without metadata such as primary keys, indexes,
and foreign keys, your reports may take too long to run, or may produce
incorrect results. If the data source does not contain the data and
metadata that you need, will it be changed, or will you work around
it?
- Does the same data exist in more than one source?
If so, choose the data source that most closely fits your
reporting requirements. If a data warehouse is available, it is typically
a better choice than an operational database. A data warehouse based
on a star schema is ideal. If this does not exist, and you expect
that your reporting application will be heavily used, consider arranging
for one to be created.
- Which data source tables are the fact tables, which are
the dimensions, and which are both fact table and dimension?
- What are the keys and attributes of each dimension?
- Which relationships are required?
- Are there multiple relationship paths between tables?
If so, what does each path represent? You must define the
preferred path for each.
Then you should review the names of data sources, tables,
and columns in your data source to ensure that you are not using names
reserved by IBM® Cognos®. If you must use a reserved word, enclose
the word in quotes in the SQL specification. For example, select
Orderdate, "Timezone". For more information, see Reserved words.