CREATE SEQUENCE SQL - Language Statements CREATE SEQUENCE Creates a new sequence number generator 1998-04-15 CREATE SEQUENCE seqname [ INCREMENT increment ] [ MINVALUE minvalue ] [ MAXVALUE maxvalue ] [ START start ] [ CACHE cache ] [ CYCLE ] 1998-09-11 seqname The name of a sequence to be created. increment The INCREMENT increment clause is optional. A positive value will make an ascending sequence, a negative one a descending sequence. The default value is one (1). minvalue The optional clause MINVALUE minvalue determines the minimum value a sequence can be. The defaults are 1 and -2147483647 for ascending and descending sequences, respectively. maxvalue Use the optional clause MAXVALUE maxvalue to determine the maximum value for the sequence. The defaults are 2147483647 and -1 for ascending and descending sequences, respectively. start The optional START start clause enables the sequence to begin anywhere. The default starting value is minvalue for ascending sequences and maxvalue for descending ones. cache The CACHE cache option enables sequence numbers to be preallocated and stored in memory for faster access. The minimum value is 1 (no cache) and this is also the default. CYCLE The optional CYCLE keyword may be used to enable the sequence to continue 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 whatever the minvalue or maxvalue is, as appropriate. 1998-09-11 status CREATE Message returned if the command is successful. ERROR: amcreate: 'seqname' relation already exists If the sequence specified already exists. ERROR: DefineSequence: START value (start) can't be > MAXVALUE (maxvalue) If the specified starting value is out of range. ERROR: DefineSequence: START value (start) can't be < MINVALUE (minvalue) If the specified starting value is out of range. ERROR: DefineSequence: MINVALUE (minvalue) can't be >= MAXVALUE (maxvalue) If the minimum and maximum values are inconsistant. 1998-09-11 CREATE SEQUENCE will enter a new sequence number generator into the current data base. This involves creating and initialising a new single block table with the name seqname. The generator will be "owned" by the user issuing the command. After the sequence is created, you may use the function nextval(seqname) to get a new number from the sequence. The function currval('seqname') may be used to determine the number returned by the last call to nextval(seqname) for the specified sequence in the current session. Use a query like SELECT * FROM sequence_name; to get the parameters of a sequence. Low-level locking is used to enable multiple simultaneous calls to a generator. 1998-09-11 Refer to the DROP SEQUENCE statement to remove a sequence. Each backend uses its own cache to store allocated numbers. Numbers that are cached but not used in the current session will be lost, resulting in "holes" in the sequence. 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 ------- 114 Use this sequence in an INSERT: INSERT INTO distributors VALUES (NEXTVAL('serial'),'nothing'); CREATE SEQUENCE is a Postgres language extension. 1998-09-11 There is no CREATE SEQUENCE statement in SQL92.