select @qty1=@qty+qty from goods2 , result 0 ?

[Shuming Wang]

Hi,
    a table goods2
  itemid  qty
  001     12.5
  002    100.0

field qty float(10,2) not null default 0
set @qty1=0
select qty, @[EMAIL PROTECTED] allqty from goods2

The result is
12.5    0
100.0   0

Why not

 12.5    12.5
100.0   112.5

?

It seems @[EMAIL PROTECTED] not work.

Best regards,
Shuming Wang