Domains are aliases for built-in data types, including precision and scale values where applicable, and optionally including DEFAULT values and CHECK conditions. Some domains, such as the monetary data types, are predefined in SQL Anywhere, but you can add more of your own.
Domains, also called user-defined data types, allow columns throughout a database to be automatically defined on the same data type, with the same NULL or NOT NULL condition, with the same DEFAULT setting, and with the same CHECK condition. Domains encourage consistency throughout the database and can eliminate some types of errors.
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