Comparison of Null Values#
Any column that does not have a value is known as being "NULL or UNKNOWN" and whenever you compare anything to a Null value the result will always be else and a NULL is not equal to another NULL.
To work around this you need detect when a column has a Null value and initialize it.
In the workflow WF_CAND_INFO there is a need to see if the stage has changed but if this is an insert or if the stage on the old record was not filled out a direct comparison of old value to new value would fail and thus process the Else. To work around this we create a variable called old_rst_id and use the operator EQNL to assign the old value (OV) of the Stage (ID) to the variable IF it is not null BUT if it is null than the value of 0 (zero) will be assigned to the old_rst_id variable.
The same could be done for the new value but if it is null the rest of the logic doesn't matter so we will want to go to the Else point anyway.
When using this technique you must always use a value that would never actually be in the field you are comparing to in order to correctly check that there was a change occurring.
