Low Performance When Using Parameterised Query

Hey...

Why do I sometimes experience low performance when I use a parameter instead
of an exact value?



For example the following performs very bad:



declare @TypeID integer

select @TypeID = 10

select ID from t_Table1 t1, t_Table2 t2 where

t_t1.ID = t_t2.FID and

t2.Type = @TypeID



but this query performs ok:

select ID from t_Table1 t1, t_Table2 t2 where

t_t1.ID = t_t2.FID and

t2.Type = 10

Jakob