add all dto fields into query object if doesn't into query NestJs

I've been working in NestJs. I try to add in the object of @Query(), all the fields that were not entered in the query:

Dto:

{
    a: number = null
    b: number = null
    c: number = null
}

Ex request:

POST url?a=5

I get:

query = {a:5}

I need:

query = {a: 5, b: null, c: null}