Final answer:
Integrity constraints in databases include CHECK constraints to validate column data, NOT NULL constraints to prevent null values, PRIMARY KEY and FOREIGN KEY constraints for entity and referential integrity, and triggers used for custom business rules resembling constraints.
Step-by-step explanation:
Major Types of Integrity Constraints
Integrity constraints are rules that ensure the accuracy and consistency of data within a relational database. The major types of integrity constraints include:
CHECK constraints: These verify that all values in a column satisfy certain conditions.
One-to-one relationships: This ensures that each row in a table is related to one, and only one, row in another table. Although important, this is typically not listed among standard integrity constraints as it pertains more to relationship integrity and database design.
NOT NULL constraints: These specify that a column must not accept NULL values, ensuring that certain important fields always contain data.
Constraints enforced with triggers: While triggers can enforce constraints, they are not constraints themselves. Triggers are procedural code that is automatically executed in response to certain events on a table or view. However, they can be used to enforce custom business rules which can act like constraints.
Typically, integrity constraints also include PRIMARY KEY constraints and FOREIGN KEY constraints, which are not specifically mentioned in the question but are crucial for maintaining entity integrity and referential integrity respectively.