Domains, Triggers, and Views

There are other features of SQL that are useful for chemical relational databases. Domains, triggers, and views are objects that belong to a schema just as tables and functions. These are also discussed in later chapters that focus on practical uses. 

An SQL domain is an extension of one of the built-in data types, but includes an optional check constraint. For example  

Create Domain smiles As Text Check (valid(Value))  

An SQL trigger is also useful to ensure that only valid data appears in a table. For example  

Create Trigger standardize Before Insert Or Update On atable For Each Row Execute Procedure standardize()  

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