Answer by Despatcher for How do I explicitly insert nulls into a parametized query?

Are you sure the params have been created by just setting the text of the SQL?

try

if Query.Params.count <> 0 then// set params..

Anyway why not make the SQL text:

'INSERT INTO crs_edocument (EDOC_ID, LINKAGE_TYPE) VALUES (999327, NULL)';

if you know the value is going to be null...