Cache and Raid performance. One of the key limitations of spinning disk hardware is the use of a physical reading armature and the time this takes to move across the surface of a diskâs platter to the required data blocks.
Constraints are part of a database schema definition. A constraint is usually associated with a table and is created with a CREATE CONSTRAINT or CREATE ASSERTION SQL statement. They define certain properties that data in a database must comply with.
A constraint *is* a requirement of sorts in the dictionary definition sense of the word (i.e., it is required), but rather than filling a business want or need, it accomodates existing systems, processes or infrastructure.