Atomic constraint:

• values cannot be broken down into other attributes of the same type
• check if that attribute can be further broken down into a relation

Key constraint

• Each primary key must be unique

Uniqueness Constraint

• All tuples must be unique
• By product of key constraint

Domain constraint

• As name suggests, the values for each attribute must meet their predefined domains

Custom domains

CREATE DOMAIN <domain_name> AS <type>
CHECK <contraint>

// Example: 
CREATE DOMAIN COMPANY_SALARY AS INTEGER
CHECK (300000 <= VALUE AND VALUE <= 2000000);

CREATE DOMAIN GPA AS DOUBLE(1, 2)
CHECK (0.0 <= VALUE AND VALUE <= 4.3);

CREATE DOMAIN WEEKDAY AS CHAR(3)
CHECK (UPPER(VALUE) IN (‘MON’, ‘TUE’, ‘WED’, ‘THU’, ‘FRI’));

Non-Null Constraint

• Essentially, some attributes are defined with the NOT NULL attribute
• Then, any insert must have a non-null value for that attribute

Entity Integrity Constraint

• The primary key being inserted can never be NULL

Referential Integrity Constraint

• Requires foreign