how to denote a duplicate value in insert?

Here is an insert statement.

insert into tableA (c1, c2, c3) values ( v1, v2, v3)

It happens v1 and v2 are the same value as (select x from tableB where x='y')

I want to avoid add select twice in the insert query. Is there a way like insert into tableA (c1, c2, c3) values ( (select x from tableB where x='y') a, a, v3)?

This is not a hard question but it’s not a duplicate either. The difference is so obvious. Sigh. Editor. Learn to read.

Answer

You seem to want insert . . . select:

insert into tableA (c1, c2, c3) 
    select x, x, 'testvalue'
    from tableB
    where x = 'y';