In Subquery with Comma Separated String

[iceangel89 LLL]

i am running this query

select sum(quantity), productid
from salesItems a, sales b
where mSalesID=52415
and a.salesID=b.salesID
and a.outletCode=b.outletCode
and customerCode='MV144653'
and productid in (select mid(packageitem, 2, length(packageitem)-2) from products where productid=54)
group by productid

the subquery

select mid(packageitem, 2, length(packageitem)-2) from products where productid=54

gives 1 row, "38,20,7"

but it seems, when using it in a subquery, mysql only evaluates it to be

select sum(quantity), productid
from salesItems a, sales b
where mSalesID=52415
and a.salesID=b.salesID
and a.outletCode=b.outletCode
and customerCode='MV144653'
and productid in (38) << so 20 and 7 missing
group by productid

i figured out this is probably due to the fact that mysql will convert the string to an int so "38"

how can i fix this so that mysql will evalaue the subquery correctly and select records where productid 38,20,7