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NOT NULL Constraint → You can impose the NOT NULL constraint on a scalar variable or constant (or scalar component of a … composite variable or constant). The NOT NULL constraint prevents assigning a value to the item … . The item can acquire this constraint either implicitly (from its data type) or explicitly. A scalar … Example 2-13, the variable
constraint → Purpose Use a constraint to define an integrity constraint— a rule that restricts the values in a … ways. The six types of integrity constraint are described briefly here and more fully in \"Semantics … \": A NOT NULL constraint prohibits a database value from being . A unique constraint prohibits
SET CONSTRAINT[S] → deferrable constraint is checked following each DML statement ( IMMEDIATE ) or when the transaction is … committed ( DEFERRED ). You can use this statement to set the mode for a list of constraint names or … . Prerequisites To specify when a deferrable constraint is checked, you must have SELECT privilege … on the table to which
Integrity Constraint States → You can specify that a constraint is enabled ( ENABLE ) or disabled ( DISABLE ). If a constraint is … conform to the constraint is prevented from being entered. If a constraint is disabled, then data that … in the table must conform to the constraint ( VALIDATE ). Conversely, if you specify NOVALIDATE
Examples of Constraint Checking → constraint makes entries in the manager_id column dependent on the values of the employee_id column … manager_id column does not have a NOT NULL constraint defined on it. Because s are allowed in foreign … Database performs its constraint checking after the statement has been completely run. To allow a row … row has 300 for employee
Deferring Constraint Checks → When the database checks a constraint, it signals an error if the constraint is not satisfied. You … until another SET CONSTRAINTS statement resets the mode. Notes: You cannot issue a SET CONSTRAINT … applies only to the current transaction. The defaults specified when you create a constraint remain … as long
Viewing Constraint Information → Oracle Database provides the following views that enable you to see constraint definitions on … ALL_CONSTRAINTS USER_CONSTRAINTS DBA view describes all constraint definitions in the database. ALL view … describes constraint definitions accessible to current user. USER view describes constraint
Reporting Constraint Exceptions → If exceptions exist when a constraint is validated, an error is returned and the integrity … constraint remains novalidated. When a statement is not successfully executed because integrity constraint … constraint until all exceptions to the constraint are either updated or deleted. To determine which
Table 5-2 Referential Integrity Constraint Terms → constraint that reference a referenced key. For example, the department_id column in employees is a foreign
Creating an Index Associated with a Constraint → Oracle Database enforces a UNIQUE key or PRIMARY KEY integrity constraint on a table by creating a … when the constraint is enabled. No action is required by you when you issue the CREATE TABLE or ALTER … exercise control over its creation. This includes both when a constraint is defined and enabled, and when a … defined but disabled
integrity constraint → Declarative method of defining a rule for a column. The integrity constraints enforce business rules and prevent the entry of invalid information into tables.
deferrable constraint → A constraint that permits a SET CONSTRAINT statement to defer constraint checking until after the … transaction is committed. A deferrable constraint enables you to disable the constraint temporarily … while making changes that might violate the constraint.
Predefined PLS_INTEGER Subtypes → Nonnegative PLS_INTEGER value NATURALN Nonnegative PLS_INTEGER value with NOT NULL constraint Foot 1 … POSITIVE Positive PLS_INTEGER value POSITIVEN Positive PLS_INTEGER value with NOT NULL constraint … PLS_INTEGER value with NOT NULL constraint. For more information, see \"SIMPLE_INTEGER Subtype of … subtype only if the value
Scalar Variable Declaration → declaration can also assign an initial value and impose the NOT NULL constraint. You reference a … types, see Chapter 3, \"PL/SQL Data Types\". NOT NULL Imposes the NOT NULL constraint on the … variable. For information about this constraint, see \"NOT NULL Constraint\". expression Value to be … \" Example 2-13,
Overview of Constraint States → basic purposes of constraints. Some of these purposes are: Enforcement In order to use a constraint for … enforcement, the constraint must be in the ENABLE state. An enabled constraint ensures that all … modification operations which produce data that violates the constraint fail with a constraint violation
Constraint States RELY NORELY → … Rewrite will then work for example in TRUSTED mode. ALTER VIEW time_view ADD (CONSTRAINT time_view_pk … PRIMARY KEY (time_id) DISABLE NOVALIDATE); ALTER VIEW time_view MODIFY CONSTRAINT time_view_pk RELY … ; ALTER TABLE sales ADD (CONSTRAINT time_view_fk FOREIGN KEY (time_id) REFERENCES time_view(time_id … ) DISABLE
Additional PL/SQL Subtypes of BINARY_FLOAT and BINARY_DOUBLE → has a NOT NULL constraint (explained in \"NOT NULL Constraint\" ). If you know that a variable will
Constant Declaration → NULL constraint. Topics Syntax Semantics Examples Related Topics Syntax constant_declaration … can be declared with an initial value. NOT NULL Imposes the NOT NULL constraint on the constant. For … information about this constraint, see \"NOT NULL Constraint\". expression Initial value for the
Declarations → Declarations Constant Declarations Initial Values of Variables and Constants NOT NULL Constraint %TYPE
%TYPE Attribute → specifies or inherits the NOT NULL constraint, you must specify an initial value for it. The %TYPE … has a NOT NULL constraint. Because surname does not inherit the NOT NULL constraint, its declaration … : surname= In Example 2-16, the variable surname inherits the data type, size, and NOT NULL constraint of