SQL databases have constraints on data types and consistency. NoSQL does away with them for the sake of speed, flexibility, and scale. One of the most fundamental choices to make when developing ...

Three types of rules can be attached to each referential constraint: an INSERT rule ... data integrity for both planned application programs and for queries in ad hoc SQL statements and BI tools.

By using cascading referential integrity constraints, you can define the actions that SQL Server 2005 takes when a user tries to delete or update a key to which existing foreign keys point.