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.
1 UNIQUE Constraint: Ensures that all values in a column are different. 2  CHECK Constraint: Makes sure that all values in a column satisfy certain criteria. 3  Primary Key Constraint: Used to uniquely identify a row in the table. 4  Foreign Key Constraint: Used to ensure referential integrity of the data.