Tech Tip: How to detect "Reject Null value inputs"

PRODUCT: 4D | VERSION: 15.2 | PLATFORM: Mac & Win

Published On: June 14, 2016

It is possible to Reject Null value inputs. In some cases it may be useful to get this information while the application is running. This can be done with SQL by querying the _USER_COLUMNS table and checking the NULLABLE field.

Field Configuration	SQL
"Reject Null value inputs" unchecked	NULLABLE="TRUE"
"Reject Null value inputs" checked	NULLABLE="FALSE"

The following method could be used to obtain this information:

C_POINTER($1)
C_BOOLEAN($0;$out)
C_TEXT($varName)
C_LONGINT($tNum;$fNum)
If (Count parameters=1)
   RESOLVE POINTER($1;$varName;$tNum;$fNum)
   Begin SQL
      select NULLABLE
      from _USER_COLUMNS
      where TABLE_ID = :$tNum
      AND COLUMN_ID = :$fNum
      into :$out;
   End SQL
   $0:=Not($out)
End if

If the method above is saved as "UTIL_DoesFieldRejectNull" then it could be used like this:

C_BOOLEAN($f)
$f:=UTIL_DoesFieldRejectNull (->[Table_1]Field_2)