De-normalize live data for the sake of reports - Good or Bad?

Question

What are the pros/cons of de-normalizing an enterprise application database because it will make writing reports easier?

Pro - designing reports in SSRS will probably be "easier" since no joins will be necessary.

Con - developing/maintaining the app to handle de-normalized data will become more difficult due to duplication of data and synchronization.

Others?

Answer 1

Denormalization for the sake of reports is Bad, m'kay.

Creating views, or a denormalized data warehouse is good.

Views have solved most of my reporting related needs. Data warehouses are great when users will be generating reports almost constantly or when your views start to slow down.

This is why you want to normalize your database

1. To free the collection of relations from undesirable insertion, update and deletion dependencies;
2. To reduce the need for restructuring the collection of relations as new types of data are introduced, and thus increase the life span of application programs;
3. To make the relational model more informative to users;
4. To make the collection of relations neutral to the query statistics, where these statistics are liable to change as time goes by.

—E.F. Codd, "Further Normalization of the Data Base Relational Model" via wikipedia

Answer 2

The only time you should consider de-normaliozation is when the time it takes the report to generate is not acceptable. De-normalization will cause consistentcy issues that are sometimes impossible to determine especially in large datasets