Null Heater, Setting database fields to NULL or DBNULL
The NULL Heater is used to explicitly assign fields to the value NULL or DBNULL. This Heater is predominantly needed when amending rows in SQL database tables (update). SQL databases have a feature where fields are initially set to a special value of DBNULL (not yet assigned). However, it is often necessary to reset a field containing data to its unassigned state and that is precisely what this Heater is intended for. When inserting rows into a database there is generally no need the use this Heater, because any values that are not determined by FlowHeater are also not specified in the database insert and therefore the field is either assumed to be NULL / DBNULL or according to the default value defined for the field (see also below).
Warning about default values
If you want to import data into an SQL database table (insert) that has default values defined and you use the NULL Heater to assign these fields, then a value of NULL or DBNULL will always be assigned; disregarding any default values defined for the database.