mirror of
https://github.com/postgres/postgres.git
synced 2025-08-09 17:03:00 +03:00
113 lines
2.7 KiB
Plaintext
113 lines
2.7 KiB
Plaintext
.\" This is -*-nroff-*-
|
|
.\" XXX standard disclaimer belongs here....
|
|
.\" $Header: /cvsroot/pgsql/src/man/Attic/create_sequence.l,v 1.2 1997/06/03 03:19:08 vadim Exp $
|
|
.TH "CREATE SEQUENCE" SQL 04/01/97 PostgreSQL PostgreSQL
|
|
.SH NAME
|
|
create sequence \(em create a new sequence number generator
|
|
.SH SYNOPSIS
|
|
.nf
|
|
\fBcreate sequence\fR seqname
|
|
[\fBincrement\fP incby_value]
|
|
[\fBminvalue\fP min_value]
|
|
[\fBmaxvalue\fP max_value]
|
|
[\fBstart\fP start_value]
|
|
[\fBcache\fP cache_value]
|
|
[\fBcycle\fP]
|
|
.fi
|
|
.SH DESCRIPTION
|
|
.BR "Create sequence"
|
|
will enter a new sequence number generator into the current data base.
|
|
Actually, new single block
|
|
.BR table
|
|
with name
|
|
.IR seqname
|
|
will be created and initialized.
|
|
The generator will be
|
|
\*(lqowned\*(rq by the user issuing the command.
|
|
.PP
|
|
The
|
|
.BR "increment"
|
|
is optional clause. Positive value will make ascending sequence,
|
|
negative - descending. Default value is 1.
|
|
.PP
|
|
The optional integer
|
|
.BR minvalue
|
|
determines the minimum value a sequence can be. Defaults are
|
|
1/-2147483647 for ascending/descending sequences.
|
|
.PP
|
|
Use optional integer
|
|
.BR maxvalue
|
|
to determine the maximum value for sequence. Defaults are
|
|
2147483647/-1 for ascending/descending sequences.
|
|
.PP
|
|
The optinal
|
|
.BR "start"
|
|
value enables sequence to begin anywhere. Default is
|
|
.BR minvalue
|
|
for ascending sequences and
|
|
.BR maxvalue
|
|
for descending ones.
|
|
.PP
|
|
The
|
|
.BR cache
|
|
option enables sequence numbers to be preallocated and
|
|
stored in memory for faster access. The minimum value is 1
|
|
(i.e. - no cache) and it is default.
|
|
.BR NOTE:
|
|
each backend uses own cache to store allocated numbers.
|
|
Cached but not used in current session numbers will be lost.
|
|
.PP
|
|
The optional
|
|
.BR cycle
|
|
keyword may be used to enable sequence to continue when the
|
|
.BR maxvalue/minvalue
|
|
has been reached by ascending/descending sequence.
|
|
If the limit is reached, the next number generated will be
|
|
whatever the
|
|
.BR minvalue/maxvalue
|
|
is.
|
|
.PP
|
|
After sequence created, You may use function
|
|
.BR nextval
|
|
with sequence name as argument to get new number from sequence
|
|
specified.
|
|
Function
|
|
.BR currval
|
|
('sequence_name')
|
|
may be used to determine number returned by last call to
|
|
.BR nextval
|
|
for specified sequence in current session.
|
|
.PP
|
|
.nf
|
|
Use query like
|
|
|
|
select * from <sequence_name>;
|
|
|
|
to get parameters of a sequence.
|
|
.fi
|
|
.PP
|
|
Low-level locking is used to enable multiple simultaneous calls
|
|
to a generator.
|
|
.PP
|
|
.SH EXAMPLES
|
|
.nf
|
|
--
|
|
-- Create sequence seq caching 2 numbers, starting with 10
|
|
--
|
|
create sequence seq cache 2 start 10;
|
|
.fi
|
|
.nf
|
|
--
|
|
-- Select next number from sequence
|
|
--
|
|
select nextval ('seq');
|
|
.fi
|
|
.nf
|
|
--
|
|
-- Use sequence in insert
|
|
--
|
|
insert into table _table_ values (nextval ('seq'),...);
|
|
.fi
|
|
.SH "SEE ALSO"
|
|
drop sequence(l).
|