it describes the instance of one entity is associated with each instances of an entity depending upon the range of cardinality constraints are two types they are minimum cardinality maximum cardinality
Constraints within a database are rules which control values allowed in columns and also enforce the integrity between columns and tables. An example of a column constraint would be a 'CHECK'...
each column contains same type of data thus when you select a data type for a particular domain then DBMS will not accept any value of other data type.Further information contributed by Ramona...
A foreign key is a type of constraint. In this example the value in a field must be the same as some value in a defined field in another table. Example in a Customer Table you might have a Column...