Match Column only if it is not empty

Question

I want to match column only if it is not empty

select *
from users
where message = 'test' AND phone like '%813%'

Where condition should be called only if phone column is not null

else below query should be called

select * from users where message = 'test'

means AND phone like '%813%' should be called only if phone is not null

Answer 1

Use CASE

select *
from users
where message = 'test' AND 
    case when phone is not null 
    then phone like '%813%'
    else 1 end