Microsoft® SQL Server 2012 Unleashed

Rules

You can use rules as another method to enforce domain integrity. Rules are similar to CHECK constraints but have some limitations. The biggest advantage when using a rule is that one rule can be bound to multiple columns or user-defined data types. This capability can be useful for columns that contain the same type of data and are found in multiple tables in a database. The syntax for creating a rule is as follows:

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CREATE RULE [ schema_name . ] rule_nameAS condition_expression[ ; ]

condition_expression can include any statement that can be placed in a WHERE clause. It includes one variable that is preceded with the @ symbol. This variable contains the value of the bound column that is supplied with the