Pivot queries or CrossTab Queries in PostgreSQL using tablefunc contrib

http://www.postgresonline.com/journal/index.php?/archives/14-CrossTab-Queries-in-PostgreSQL-using-tablefunc-contrib.html

The generic way of doing cross tabs (sometimes called PIVOT queries) in an ANSI-SQL database such as PostgreSQL is to use CASE statements which we have documented in the article What is a crosstab query and how do you create one using a relational database?.

In this particular issue, we will introduce creating crosstab queries using PostgreSQL tablefunc contrib.