DELETE removes one or more records in a table, checking referential
Constraints (to see if there are dependent child records) and firing any
DELETE triggers....
Never. New primary key values are not a problem. However, the values of foreign key inserts must have corresponding primary key values in their related tables...
"Mutating" means "changing". A mutating table is a table that is currently being modified by an update, delete, or insert statement. When a trigger tries to ref...
Triggers are special kind of stored procedures that get executed automatically when an INSERT, UPDATE or DELETE operation takes place on a table.
Triggers ca...
There are two Integrity rules.
Ø Entity Integrity: States that “Primary key cannot have NULL value”
Ø Referential Integrity: States that “Foreign Key...
Maintaining data integrity through a set of rules that restrict the values of one or more columns of the tables based on the values of primary key or unique...
Unlike Relational systems in System R
Domains are not supported
Enforcement of candidate key uniqueness is optional
Enforcement of entity integrity is option...