UserDisplayName

String (90)

On Insert: Yes

On Update: Yes (if UserReferenceSystemId and UserUid is not supplied)

The user display name is a unique identifier for a user

UserId

Int32

On Insert: No

On Update: No

The user Id is a unique identifier for a user. For internal use only.

UserReferenceSystemId

String (20)

On Insert: No

On Update: Yes (if UserDisplayName and UserUid is not supplied)

The user reference system Id / employee Id  is a unique identifier for a user

UserUid

Int64

On Insert: No

On Update: Yes (if UserDisplayName and UserReferenceSystemId is not supplied)

The user Uid is a unique and immutable identifier for a user

1152921504607112369

EmailAddress

String (100)

On Insert: Yes

On Update: No

The user email address is a unique identifier for a user

FirstName

String (20)

On Insert: Yes

On Update: No

The user's first name

LastName

String (20)

On Insert: Yes

On Update: No

The user's last name

MiddleName

String (20)

On Insert: Yes

On Update: No

The user's middle name