Dear Helen,

Thank you for your quick reply.

You wrote many things which it looks general problem on my side.
But I don't know how can I solve the parameter problem?

I think you know (better than me) when we use outer join.(We want to
show all items) This is the reason why i use it.
The SQL.Text not showed all of the used columns.

KeyLinks is ITEMS.ID which unique and never null.

In the system it possible to create many hierarchies, which selectable
from lookupcombo.
But this lookup not connected to the query.
When this lookup change the system sets the parameter. (and make a
refresh)

But when I change the order why will be empty string the value of
parameter?
How can I solve this problem?

Thanks again your suggests.
Endre