Here's another possibility:

declare @t1 table (Id int)

insert into @t1 (Id)

select 1 union

select 2 union

select 3

declare @t2 table (Id int, X int)

insert into @t2 (Id, X)

select 1, 10 union

select 2, 5 union

select 3, 0;

with t3 as (

select id, x, row_number() over (partition by id order by id) ro from @t2

cross join sys.all_columns

)

select id, x from t3 where ro <= x