Required Fields

Required fields must have a non-null value. This rule affects the create() and update() calls:

• When a client application invokes the create() call, Salesforce.com automatically populates the data for certain required fields (such as system fields and the object ID fields). Similarly, if a required field has a default value (its defaultedOnCreate attribute is set to true, as described in Field, then Salesforce.com implicitly assigns a value for this field when the object is created, even if a value for this field is not explicitly passed in on the create() call. For all other required fields, such as ID fields that are analogous to foreign keys in SQL (see Reference Field Type), a client application must explicitly assign a value when the object is created (it cannot be null).
• When a client application invokes the update() call, a required field cannot be set to null. Many required fields cannot be changed in an update() call.

Any field not specified as required in the object description is optional, that is, it can be null when updated or created.

For more information about the special handling of required fields for particular objects, see the documentation for such objects later in this topic.