Re: How can I replace the year of the created_at column with the current year dynamically ?

Here is my try :

staging::=> select  to_char(created_at,'DD/MM') || '/' || to_char(now(),'YYYY') as when from users;

    when    

------------

 24/02/2014

...

 20/02/2014

(15 rows)

Can the same be done using any other clever trick ? 

No tricks are springing to mind but a warning is. The above will produce illegal dates whenever you are an inconvenient number of years past February 29. I think this will fix that issue:

select created_at + ((extract(year from now()) - extract(year from created_at)) * '1 year'::interval);

Note that the above returns a date (assuming that created_at is a date). You may need to apply to_char to format to your desired specification.

Cheers,
Steve