When creating tables in a database, you often need to define rules regarding the values allowed in columns (fields). As mentioned in Chapter 19, constraints allow you to enforce integrity by creating rules for a table. The five types of constraints are listed below.
Identifies the column or set of columns whose values uniquely identify a row in a table.
Defines the relationship between tables and maintains data integrity when records are being added, changed, or deleted in a table.
Ensures that no duplicate values are entered in a specific column or combination of columns that is not ...