A
sequence
in PostgreSQL is a database object that is essentially an automatically incrementing
numeric value. For this reason, sequences are commonly known in other database products as
auto-increment
values. Sequences can be extremely useful in assigning non-random, unique identification numbers to tables that require
such values.
A sequence consists of a current numeric value, and a set of characteristics that determine how to automatically increment
(or alternatively, decrement) that value upon use.
Along with its current value, a sequence also includes a minimum value, a maximum value, a starting value, and the
amount
to increment the sequence by. This increment is usually 1, but may be
any whole integer.
In practice, sequences are not meant to be accessed directly. Instead, they are used through a set of functions built
into PostgreSQL which either set, increment, or return the current value of the sequence.
Creating a sequence
Sequences are created with the CREATE SEQUE…
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