The relation attribute @ONNOVALUE is used to define an error if no value can be selected from a Telitab data set.

Syntax

Place @ONNOVALUE:ParameterName,MessageCaption[,Action] in the data slot of the relation

Arguments

ParameterName defines the parameter containing the error message. You can also directly type the message between quotes.
MessageCaption is the caption of the message box presenting the error.
Action is optional, when no action is given, Quaestor will stop. When continue is written, Quaestor will continue after the message.

This attribute can be for instance be placed in a relation that uses the PARSE#() function to parse external data. The moment some of the data is missing, an error message can be raised.
This attribute can also be placed in the GET$() function to catch the error when an external process stops without providing output (which you expected to receive). When you do not expect to receive the output, use @OUTPUTNONE in that case Quaestor will not wait for the process and simply continue. However, realise that the latter is not an error catcher while the above can be used as such.

Member of functional group: Modeling