Rules are a
backward-compatibility
feature that performs some of the same functions as
CHECK
constraints.
CHECK
constraints are the
preferred, standard way to
restrict the values in a column.
CHECK
constraints are also more concise than rules; there can only be one rule applied to a column, but multiple
CHECK
constraints can be applied.
CHECK
constraints are specified as part of the
CREATE TABLE
statement, while rules are created as separate objects and then bound to the column.
Important about RULE:
This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.
Refer:
http://technet.microsoft.com/en-us/library/ms188064(v=sql.105).aspx[
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