An integrity constraint is a declarative way to define a business rule for a column of a table. If an integrity constraint is created for a table and some existing table data does not satisfy the constraint, then the constraint can not be enforced. After a constraint is defined, if any of the results of a DML statement violate the integrity constraint, then the statement is rolled back, and an error is returned. Integrity constraint are defined with a table and are stored as part of the table’s definition in the data dictionary.
Supported Integrity constraint:
1. NOT NULL
2. UNIQUE KEY
3. CHECK.
4. PRIMARY KEY
5. FOREIGN KEY
Key is used in the definitions of several types of integrity constraints. Different types of keys include:
1. Primary Key
2. Unique Key
3. Foreign Key
4. Referenced Key
Triggers
Triggers are procedures written in PL/SQL, java or C that run (fire) implicitly whenever a table or view is modified or when some user actions or database system actions occur.
SQL Statement categories:
Data definition Language (DDL) Statements
Data Manipulation Language (DML) Statements
Transaction Control Statements
Session Control Statements
System control Statements
Embedded SQL statements