When users enter data in a DataWindow object, you want to be sure the data is valid before using it to update the database. Validation rules provide one way to do this.
You usually define validation rules in the Database painter. To use a validation rule, you associate it with a column in the Database painter or DataWindow painter.
Another technique
You can also perform data validation through code tables, which are implemented through a column's edit style.
For more information, see About edit styles.
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 Using DataWindow Objects in DataWindow Programmers Guide.
At 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 section called “GetValidate” in DataWindow Reference and the section called “SetValidate” in DataWindow Reference.
