Question

What are SQL triggers used for?

1) Providing default values
2) Validity checking
3) Updating views
4) Performing referential integrity actions

Answer 1

SQL triggers are used for validity checking, performing referential integrity actions, providing default values, and updating views within a database. They act as automatic procedures that fire upon certain database events to maintain data integrity and enforce business rules.

Step-by-step explanation:

SQL triggers are special stored procedures that are automatically executed or fired when certain events occur in a database. They are typically used for:

• Validity checking: To ensure that data modifications are correct.
• Performing referential integrity actions: To maintain consistency across related tables.
• Providing default values: To set defaults when data is inserted into a database without specifying all values.
• Updating views: To refresh materialized views when underlying data changes.

For instance, a trigger could be used to check the validity of data by comparing new entries against business rules, or to perform cascading updates when a foreign key is modified, ensuring referential integrity. Triggers can also automatically populate fields with default values if none are provided during data insertion.