Field.ValidationRule Property (DAO)

Sets or returns a value that validates the data in a field as it's changed or added to a table (Microsoft Access workspaces only). Read/write String.

Syntax

expression .ValidationRule

expression An expression that returns a Field object.

Remarks

The settings or return values is a String that describes a comparison in the form of an SQL WHERE clause without the WHERE reserved word. For an object not yet appended to the Fields collection, this property is read/write.

The ValidationRule property determines whether or not a field contains valid data. If the data is not valid, a trappable run-time error occurs. The returned error message is the text of the ValidationText property, if specified, or the text of the expression specified by ValidationRule.

For a Field object, use of the ValidationRule property depends on the object that contains the Fields collection to which the Field object is appended.

Validation is supported only for databases that use the Microsoft Access database engine.

The string expression specified by the ValidationRule property of a Field object can refer only to that Field. The expression can't refer to user-defined functions, SQL aggregate functions, or queries. To set a Field object's ValidationRule property when its ValidateOnSet property setting is True, the expression must successfully parse (with the field name as an implied operand) and evaluate to True. If its ValidateOnSet property setting is False, the ValidationRule property setting is ignored.