column constrainsts

NOVALIDATE

When you create a foreign key constraint in Oracle, the database ensures that the values in the foreign key column match the values in the referenced primary key column. However, there are situations where you might want to create a foreign key constraint without immediately validating existing data. NOVALIDATE Behavior ENABLE VALIDATE ENABLE NOVALIDATE   […]

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Table Constraint Examples

— column-level primary key constraint named OUT_TRAY_PK: START TRANSACTION; CREATE TABLE TBL_SAMPLE_FLIGHTS ( SENT TIMESTAMP, DESTINATION CHAR(8), SUBJECT CHAR(64) NOT NULL CONSTRAINT OUT_TRAY_PK PRIMARY KEY, NOTE_TEXT VARCHAR(3000) ); COMMIT; INSERT INTO TBL_SAMPLE_FLIGHTS( SENT, DESTINATION, SUBJECT, NOTE_TEXT ) VALUES( SYSDATE, ‘Atlanta’, ‘Note to other attendants’, ‘This is how this passanger wants to be treated on the

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CONSTRAINT CLAUSE

What is a constraint? A CONSTRAINT clause is an optional part of a CREATE TABLE statement or ALTER TABLE statement. A constraint is a rule to which data must conform. Constraint names are optional. Types of Constraints Column constraints and table constraints have the same function; the difference is in where you specify them. a column-level constraint Column-level

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