Constraints enforce rules at the table level.
Constraints prevent the deletion of table if there are dependencies.
The following constraint types are valid.
- NOT NULL : A NOT NULL constraint prohibits a database value from being null.
-UNIQUE : A unique constraint prohibits multiple rows from having the same value in the
same column or combination of columns but allows some values to be null.
-PRIMARY KEY : Uniquely identifies each row in the table.
-FOREIGN KEY : Establishes and Enforces a foreign key relationship between the column and a column of the referenced table.
-CHECK : Specifies a condition that must me true.
•Name the constraints or the oracle server generates a name by using Sys_Cn format.
• Create a constraint either,at the time the table is created or after the table has been created.
• Define a constraint at the column or table level.
• View constraints in the data dictionary ( USER_CONSTRAINTS )
Constraints prevent the deletion of table if there are dependencies.
The following constraint types are valid.
- NOT NULL : A NOT NULL constraint prohibits a database value from being null.
-UNIQUE : A unique constraint prohibits multiple rows from having the same value in the
same column or combination of columns but allows some values to be null.
-PRIMARY KEY : Uniquely identifies each row in the table.
-FOREIGN KEY : Establishes and Enforces a foreign key relationship between the column and a column of the referenced table.
-CHECK : Specifies a condition that must me true.
•Name the constraints or the oracle server generates a name by using Sys_Cn format.
• Create a constraint either,at the time the table is created or after the table has been created.
• Define a constraint at the column or table level.
• View constraints in the data dictionary ( USER_CONSTRAINTS )
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