Introduction to Oracle9i: SQL (11)

Including constraints
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• In order to view Null values as some other character the command ‘Set Null ’ has to be specified before execution of the select statement. Eq. SET NULL #.
• Constraints have functions to enforce rules at the view and table levels and to prevent the deletion of data if dependencies exist between tables. Constraints are used to put dependences on data.
• ‘Disable Constraint’ disables the constraint, drop the index on the table and does not allow any DML operation on the table.
• Oracle creates a profile named DEFAULT when the database is created. Profile cannot be renamed. Default is a valid name for a profile resource. When a database is created all resources associated with the default profile is unlimited.