A check constraint limits the values that a column accepts, defined by a logical expression. Any attempt to insert or update a value outside the range of accepted values is rejected.

Check constraints can be specific to one column or multiple columns; further, a single column can have multiple constraints. Defining a check constraint on a table can limit the values for certain columns based on the values of other columns.

Class RWDBCheckConstraint encapsulates a check constraint based on the expression defined by an RWDBExpr object. RWDBCheckConstraintList holds any number of RWDBCheckConstraint instances. An RWDBSchema object always contains a single RWDBCheckConstraintList containing zero or more check constraints relevant to that schema.