Creating Sequences

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A sequence can be used to provide the default value for a domain or a table column, etc.

A sequence returns a series of integer values which is defined by specifying an initial value, a maximum value, an increment and whether the sequence is to be unique or not.

A sequence that has been initialized has a current value, which is returned from the function CURRENT_VALUE. The function NEXT_VALUE is used to initialize a sequence and to subsequently advance the current value of the sequence through its defined series of values.

A unique sequence will never return the same value twice.

Examples of Sequences

Create a sequence that returns odd numbers:

 CREATE SEQUENCE seq_1 INITIAL_VALUE = 1 INCREMENT = 2 IN DATABANK userdb;

Create a sequence that defines the following series of values: 1, 4, 7, 10, 3, 6, 9, 2, 5, 8:

 CREATE UNIQUE SEQUENCE seq_2
    INITIAL_VALUE = 1
    INCREMENT = 3
    MAX_VALUE = 10
    IN DATABANK userdb;

Create a table that uses a sequence to set a column default value:

 CREATE TABLE objinfo (objid INTEGER DEFAULT NEXT_VALUE OF obj_seq,
                       description NCHAR VARYING(1000));

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