How do I select the value with SERIAL data type in postgres I want to know how to select values from a column that has SERIAL data type.

I already try to do that but the output is like this 'Resource id #3', and not just '3'

I use SERIAL so I dont have to input ID like when I use integer
There is no actual serial data type. serial is just a notational convenience.
The resulting data type is integer for serial or bigint for bigserial

Related answer on SO with more details:
Auto increment SQL function

You'd have to be more specific for a more specific answer.