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CREATE SEQUENCE(7)               SQL Commands               CREATE SEQUENCE(7)



NAME
       CREATE SEQUENCE - define a new sequence generator


SYNOPSIS
       CREATE [ TEMPORARY | TEMP ] SEQUENCE name [ INCREMENT [ BY ] increment ]
           [ MINVALUE minvalue | NO MINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE ]
           [ START [ WITH ] start ] [ CACHE cache ] [ [ NO ] CYCLE ]
           [ OWNED BY { table.column | NONE } ]


DESCRIPTION
       CREATE  SEQUENCE creates a new sequence number generator. This involves creating and initializing a new special
       single-row table with the name name. The generator will be owned by the user issuing the command.

       If a schema name is given then the sequence is created in the specified schema. Otherwise it is created in  the
       current  schema.  Temporary sequences exist in a special schema, so a schema name cannot be given when creating
       a temporary sequence.  The sequence name must be distinct from the name of any other sequence, table, index, or
       view in the same schema.

       After  a  sequence  is  created, you use the functions nextval, currval, and setval to operate on the sequence.
       These functions are documented in in the documentation.

       Although you cannot update a sequence directly, you can use a query like:

       SELECT * FROM name;

       to examine the parameters and current state of a sequence. In particular, the last_value field of the  sequence
       shows  the  last  value  allocated  by  any  session. (Of course, this value might be obsolete by the time it's
       printed, if other sessions are actively doing nextval calls.)

PARAMETERS
       TEMPORARY or TEMP
              If specified, the sequence object is created only for this session, and is automatically dropped on ses-
              sion  exit.  Existing permanent sequences with the same name are not visible (in this session) while the
              temporary sequence exists, unless they are referenced with schema-qualified names.

       name   The name (optionally schema-qualified) of the sequence to be created.

       increment
              The optional clause INCREMENT BY increment specifies which value is added to the current sequence  value
              to  create  a  new  value. A positive value will make an ascending sequence, a negative one a descending
              sequence. The default value is 1.

       minvalue

       NO MINVALUE
              The optional clause MINVALUE minvalue determines the minimum value a  sequence  can  generate.  If  this
              clause  is  not supplied or NO MINVALUE is specified, then defaults will be used. The defaults are 1 and
              -263-1 for ascending and descending sequences, respectively.

       maxvalue

       NO MAXVALUE
              The optional clause MAXVALUE maxvalue determines the maximum value for the sequence. If this  clause  is
              not  supplied  or NO MAXVALUE is specified, then default values will be used. The defaults are 263-1 and
              -1 for ascending and descending sequences, respectively.

       start  The optional clause START WITH start  allows the sequence to begin anywhere. The default starting  value
              is minvalue for ascending sequences and maxvalue for descending ones.

       cache  The optional clause CACHE cache specifies how many sequence numbers are to be preallocated and stored in
              memory for faster access. The minimum value is 1 (only one value can be generated at a  time,  i.e.,  no
              cache), and this is also the default.

       CYCLE

       NO CYCLE
              The CYCLE option allows the sequence to wrap around when the maxvalue or minvalue has been reached by an
              ascending or descending sequence respectively. If the limit is reached, the next number  generated  will
              be the minvalue or maxvalue, respectively.

              If  NO  CYCLE  is  specified, any calls to nextval after the sequence has reached its maximum value will
              return an error. If neither CYCLE or NO CYCLE are specified, NO CYCLE is the default.

       OWNED BY table.column

       OWNED BY NONE
              The OWNED BY option causes the sequence to be associated with a specific table column, such that if that
              column  (or  its whole table) is dropped, the sequence will be automatically dropped as well. The speci-
              fied table must have the same owner and be in the same schema as  the  sequence.   OWNED  BY  NONE,  the
              default, specifies that there is no such association.

NOTES
       Use DROP SEQUENCE to remove a sequence.

       Sequences  are  based  on  bigint  arithmetic,  so  the  range cannot exceed the range of an eight-byte integer
       (-9223372036854775808 to 9223372036854775807). On some older platforms, there might be no compiler support  for
       eight-byte integers, in which case sequences use regular integer arithmetic (range -2147483648 to +2147483647).

       Unexpected results might be obtained if a cache setting greater than one is used for  a  sequence  object  that
       will be used concurrently by multiple sessions. Each session will allocate and cache successive sequence values
       during one access to the sequence object and increase the sequence object's last_value accordingly.  Then,  the
       next  cache-1  uses  of  nextval within that session simply return the preallocated values without touching the
       sequence object. So, any numbers allocated but not used within a session will be lost when that  session  ends,
       resulting in ''holes'' in the sequence.

       Furthermore,  although  multiple sessions are guaranteed to allocate distinct sequence values, the values might
       be generated out of sequence when all the sessions are considered. For example, with a  cache  setting  of  10,
       session  A  might  reserve  values  1..10  and return nextval=1, then session B might reserve values 11..20 and
       return nextval=11 before session A has generated nextval=2. Thus, with a cache setting of one  it  is  safe  to
       assume  that  nextval  values are generated sequentially; with a cache setting greater than one you should only
       assume that the nextval values are all distinct,  not  that  they  are  generated  purely  sequentially.  Also,
       last_value  will  reflect  the latest value reserved by any session, whether or not it has yet been returned by
       nextval.

       Another consideration is that a setval executed on such a sequence will not be noticed by other sessions  until
       they have used up any preallocated values they have cached.

EXAMPLES
       Create an ascending sequence called serial, starting at 101:

       CREATE SEQUENCE serial START 101;


       Select the next number from this sequence:

       SELECT nextval('serial');

        nextval
       ---------
            101


       Select the next number from this sequence:

       SELECT nextval('serial');

        nextval
       ---------
            102


       Use this sequence in an INSERT command:

       INSERT INTO distributors VALUES (nextval('serial'), 'nothing');


       Update the sequence value after a COPY FROM:

       BEGIN;
       COPY distributors FROM 'input_file';
       SELECT setval('serial', max(id)) FROM distributors;
       END;


COMPATIBILITY
       CREATE SEQUENCE conforms to the SQL standard, with the following exceptions:

       ? The standard's AS <data type> expression is not supported.

       ? Obtaining  the  next  value  is  done  using  the nextval() function instead of the standard's NEXT VALUE FOR
         expression.

       ? The OWNED BY clause is a PostgreSQL extension.


SEE ALSO
       ALTER SEQUENCE [alter_sequence(7)], DROP SEQUENCE [drop_sequence(7)]



SQL - Language Statements         2014-02-17                CREATE SEQUENCE(7)