Pro SQL Server Relational Database Design and Implementation, Fifth Edition

ALTER TABLE Messages.Topic   ADD CONSTRAINT CHKTopic_Name_NotEmpty       CHECK (LEN(RTRIM(Name)) > 0);ALTER TABLE Messages.MessageTopic   ADD CONSTRAINT CHKMessageTopic_UserDefinedTopicName_NotEmpty       CHECK (LEN(RTRIM(UserDefinedTopicName)) > 0);

The other domain we specifically mentioned was for the UserHandle, as repeated in Table 6-9.

Table 6-9. Domain: UserHandle

Property	Setting
Name	UserHandle
Optional	No
Datatype	Basic character set, maximum of 20 characters
Value Limitations	Must be 5–20 simple alphanumeric characters and start with a letter
Default Value	n/a

To implement this domain, things get a bit more interesting:

ALTER TABLE Attendees.MessagingUser  ADD CONSTRAINT CHKMessagingUser_UserHandle_LengthAndStart     CHECK (LEN(Rtrim(UserHandle)) ...