Error: Types don't match between the anchor and the recursive part , recursive cte for decimal datatype

Question

I have something as the below

declare @t table (id int identity,Price decimal(6,2))
insert into @t
    select 17.5 union all 
    select 10.34 union all 
    select 2.0 union all 
    select 34.5

Now if I write a query as below

;with cte(id, price) as 
(
    select id, price
    from @t 
    union all
    select cte.id, cte.price + t.price
    from cte 
        join @t t
           on cte.id < t.id
)
select *
from @t

I am getting the below error at runtime:

Types don't match between the anchor and the recursive part....

I even tried the same after typecasting(to decimal) but with same result ....

However, if I typecast to int it works... but that should not be the case (:

Answer 1

The fix:

;with cte(id,price) as 
(
    Select id, price from @t 
    Union all
    Select cte.id, cast(cte.price + t.price as decimal(6,2))
    From cte 
    Join @t t
    On cte.id < t.id
)
Select * from @t

Explanation:

The expression cte.price + t.price will return the type that is not necessarily decimal(6,2), can return decimal(5,2). So it cannot union those two values after that.