postman add variable code example

Example 1: postman environment variables in body

{ "customer_id" : "{{cust_id}}" }

Example 2: Postman Variables

just like variables in Java. 
we can create variables in postman to reuse the value 
1.Global variables: accessible everywhere in same workspace 
2.Environment variables: accessible in selected environment 
3.Collection Variables: belong to the collection itself and 
only accessible within the collection

Example 3: collection variable api

Only accessible within the same collection and
can not be accessed anywhere else
COLLECTION variables are available throughout 
the requests in a collection and are independent
of environments, so do not change based on the selected environment.
I use collection variables when
I use single environment like url details.
We can refer to the variable by using {{}}(double curly brace)
and  it can be used anywhere