Constraints can be created at the same time as the

Constraints can be created at the same time as the table is created (using CREATE
TABLE) or after the table has been created (using ALTER TABLE)
Sequences:
• Automatically generates unique numbers.
• Is sharable object. (used by multiple users)
• Is typically used to create a primary key value.
• Save time to write application code to generate unique numbers.
• Speeds up the efficiency of accessing sequence values when cached in memory.
Syntax:
CREATE SEQUENCE sequence_name
[INCREMENT BY n ]
[START WITH n ]
[{MAXVALUE n | NOMAXVALUE } ]
[{MINVALUE n | NOMINVALUE } ]

[{CYCLE | NOCYCLE } ]
[{CACHE n | NOCACHE} ]
• Sequence name follows the same rule as the Table Name or Constraint Name (start with a
letter, max length 30 characters).
• If INCREMENT BY is omitted, default is 1, negative n means decreasing.
• If START WITH is omitted, default is 1.
• MAXVALE/MINVALUE specifies the maximum/minimum value of the sequence. The
default is NO for both.
• By default, no CYCLE. Oracle cache 20 values.
Alter Sequence
ALTER SEQUENCE sequence_name
[INCREMENT BY n ]
[{MAXVALUE n | NOMAXVALUE} ]
[{MINVALUE n | NOMINVALUE} ]
[{CYCLE | NOCYCLE} ]
[{CACHE n | NOCACHE} ]