Understanding validation rules

Validation rules are criteria that a DataWindow object uses to validate data entered into a column by users. They are PowerBuilder-specific and therefore not enforced by the DBMS.

Validation rules assigned in the Database painter are used by default when you place columns in a DataWindow object. You can override the default rules in the DataWindow painter.

A validation rule is an expression that evaluates to either “true” or “false”. If the expression evaluates to “true” for an entry into a column, PowerBuilder accepts the entry. If the expression evaluates to “false”, the entry is not accepted and the ItemError event is triggered. By default, PowerBuilder displays a message box to the user. You can customize the message displayed when a value is rejected.

You can also code the ItemError event to cause different processing to happen.

For more information, see the chapter on using DataWindow objects in the DataWindow Programmers Guide.

NoteAt runtime In scripts, you can use the GetValidate method to obtain the validation rule for a column and the SetValidate method to change the validation rule for a column.

For information about the GetValidate and SetValidate methods, see the online help.