Definitions

A   B   C   D   E   F   G   H   I   J   K   L   M   N   
O   P   Q   R   S   T   U   V   W   X   Y   Z

C

CHECK Constraint
It enforces integrity by restricting the values to be inserted in a column. It defines a condition that each row must sastisfy. You can define multiple check constraints on a single column. Also, you can apply a single check constraint to multiple columns.

E

Exception
An exception is an error in PL/SQL that is raised during the execution of a block of code. PL/SQL allows you to handle exceptions efficiently. You can define separate blocks for dealing with exceptions.

F

FOREIGN KEY Constraint
It designates a column or a combination of columns as a foreign key. It establishes a relationship between a primary key or a unique key in the same table or different table. A foreign key enforces that the value within the column matches the value in the relationship column.

N

NOT NULL Constraint
It ensures that the column contains no null values. After you define a column as not null, it becomes a mandatory column. Columns without the NOT NULL constraint can contain null values by default.

P

PRIMARY KEY Constraint
It is a column or a set of columns that uniquely identifies each row in a table. This constraint enforces uniqueness of the column or column combination. It ensures that no column that is part of the primary key can contain a null value. A null value is essentially a blank.

Public Components
Public components are declared in the package specification. The specification defines a public application programming interface (API) for users of package features and functionality. That is, public components can be referenced from any Oracle server environment that is external to the package.

Private Components
Private components are placed in the package body and can be referenced only by other constructs within the same package body. Private components can reference the package public components.

R

Row trigger
A row trigger executes once for each row affected by the triggering event. A row trigger is not executed if the triggering event does not affect any rows. To indicate a row trigger, the FOR EACH ROW clause is specified.

S

Statement trigger
A statement trigger is the default type of trigger and executes once for the triggering event. A statement trigger fires even if now rows are affected at all.

U

UNIQUE Constraint
It specifies that no two rows of a table can have duplicate values in a specified column or a set of columns. A table can have more than one unique key. If the UNIQUE constraint comprises more than one column, then the group of columns is called a composite key.