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.
Column and Table Constraints. Constraints can be column constraints or table constraints. A column constraint is specified as part of a column definition and applies only to that column. The constraints in the previous examples are column constraints.QL Server supports the following classes of constraints: NOT NULL specifies that the column does not accept NULL values. For more information, see Allowing Null Values. CHECK constraints enforce domain integrity by limiting the values that can be put in a column. For more information, see CHECK Constraints.