I have defined a DB Source with an int "ID" column which is Primary Key, and datetime "CompletionTime" column which may have "null" value.
I linked such two columns with the two columns of a dinamic repeating table.
The solution correctly loads and display records from database. Displaying the correct timestamp for non-null records and blank for null records, as I expcted.
I defined "Control Action on label clicked" as follows:
Update Node(s) @CompletionTime
with result of concat(current-date-no-TZ(), 'T', current-time-no-TZ())
If I run the simulation, when I tap on a "CompletionTime" label bearing a blank value it retuns « Cannot Update Node '@StepCompletato' (no 'Target Node' found) »
I have bypassed the problem adding "Ensure exist on load (fixed value)" (value = "1970-01-10T00:00:00"), but - of course - on submitting changes to database, this subsitutes "null" values of un-tapped records with "1970-01-10T00:00:00".
Is there a value for managing null values to substitute some of them with a real timestamp while leaving others unchanged?