Constraints ("M" Programming Guide)

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A constraint is a predicate or Boolean function that restricts the values allowed in a particular context. Constraints are commonly applied to fields and types. A constraint can be defined at the type level or on individual fields. Constraints are applied by using the where key word.

Constraints also occur inside computed values, when you specify a view using the select statement.

In This Section

• Constraints on Types
  Describes how to apply a predicate to a type using the where keyword.

• where ("M" Reference)
  Describes how to use the where keyword.