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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
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
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
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
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
Enable Novalidate Constraint State → When a constraint is in the enable novalidate state, all subsequent statements are checked for … conformity to the constraint. However, any existing data in the table is not checked. A table with … that are uploading valid OLTP data. Enabling a constraint does not require validation. Enabling a … constraint novalidate
Specifying the Index Associated with a Constraint → constraint Specify a CREATE INDEX statement that the database is to use to create the index and … enforce the constraint These options are specified using the USING INDEX clause. The following statements … on a (a1))); Example 2: CREATE TABLE b( b1 INT, b2 INT, CONSTRAINT bu1 UNIQUE (b1, b2) USING INDEX … (create unique index
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
Constraint Attributes → initially immediate. These attributes can be different for each constraint. You specify them with … keywords in the CONSTRAINT clause: DEFERRABLE or NOT DEFERRABLE INITIALLY DEFERRED or INITIALLY … constraint's attributes. See Also: Oracle Database SQL Language Reference for information about constraint attributes and their default values
Constraint States → ENABLE ensures that all incoming data conforms to the constraint DISABLE allows incoming data … , regardless of whether it conforms to the constraint VALIDATE ensures that existing data conforms to the … constraint NOVALIDATE means that some existing data may not conform to the constraint In addition … : ENABLE
Specifying Storage Options for an Index Associated with a Constraint → using the USING INDEX clause. The following CREATE TABLE statement enables a PRIMARY KEY constraint
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 NOVALIDATE);
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
Deferred Constraint Checking → You can defer checking constraints for validity until the end of the transaction. A constraint is … deferred if the system checks that it is satisfied only on commit. If a deferred constraint is … violated, then commit causes the transaction to undo. If a constraint is immediate (not deferred), then it … immediately. If a constraint
The Mechanisms of Constraint Checking → table has been defined as in Figure 21-2. The self-referential constraint makes the entries in the … a NOT NULL constraint defined on it. Because s are allowed in foreign keys, this row is … case reveals that Oracle Database performs its constraint checking after the statement has been … might have empno as 300 and mgr as 200.
Default Column Values and Integrity Constraint Checking → … Therefore, default column values are subject to all integrity constraint checking.
Constraint Checking During Defining → OCI_ATTR_MAXCHAR_SIZE value on the define buffer to impose an additional character length constraint. There … the byte constraint. Dynamic SQL Selects When sizing buffers for dynamic SQL, always use the … you can use the OCI_ATTR_MAXCHAR_SIZE value to set an additional constraint on the define buffer. A
11.2.2 Creating Constraint Documents → Constraint documents define one or more constraint rules. The XML schema ordcmct.xsd defines the … XML schema that constrains constraint documents. (See Section B.2 for a listing of the constraint … document schema ordcmct.xsd.) The default constraint documents ( ordcmct.xml, ordcmcmd.xml … constraint
The Execution Model for Triggers and Integrity Constraint Checking → When a statement in a trigger body causes another trigger to fire, the triggers are said to be cascading. Oracle Database allows up to 32 triggers to cascade at simultaneously. A relational database does not guarantee the order of rows processed by a SQL statement. Therefore, do not create triggers that depend on the order in which rows are processed. See Also: Oracle Database PL/SQL Language Reference