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<REFENTRY ID="SQL-CREATESEQUENCE">
<REFMETA>
<REFENTRYTITLE>
CREATE SEQUENCE
</REFENTRYTITLE>
<REFMISCINFO>SQL - Language Statements</REFMISCINFO>
</REFMETA>
<REFNAMEDIV>
<REFNAME>
CREATE SEQUENCE
</REFNAME>
<REFPURPOSE>
Creates a new sequence number generator
</REFPURPOSE>
<REFSYNOPSISDIV>
<REFSYNOPSISDIVINFO>
<DATE>1998-04-15</DATE>
</REFSYNOPSISDIVINFO>
<SYNOPSIS>
CREATE SEQUENCE <replaceable class="parameter">seqname</replaceable>
[INCREMENT <replaceable class="parameter">increment</replaceable>]
[MINVALUE <replaceable class="parameter">minvalue</replaceable>]
[MAXVALUE <replaceable class="parameter">maxvalue</replaceable>]
[START <replaceable class="parameter">start</replaceable>]
[CACHE <replaceable class="parameter">cache</replaceable>]
[CYCLE]
</SYNOPSIS>
<REFSECT2 ID="R2-SQL-CREATESEQUENCE-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Inputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">seqname</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The name of a sequence to be created.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">increment</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The <option>INCREMENT <replaceable class="parameter">increment</replaceable></option> clause is optional. A positive value will make an
ascending sequence, a negative one a descending sequence. The default value
is 1.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">minvalue</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The optional clause <option>MINVALUE
<replaceable class="parameter">minvalue</replaceable></option>
determines the minimum value
a sequence can be. The defaults are 1 and -2147483647 for
ascending and descending sequences, respectively.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">maxvalue</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Use the optional clause <option>MAXVALUE
<replaceable class="parameter">maxvalue</replaceable></option> to
determine the maximum
value for the sequence. The defaults are 2147483647 and -1 for
ascending and descending sequences, respectively.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">start</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The optional <option>START
<replaceable class="parameter">start</replaceable>
clause</option> enables the sequence to begin anywhere.
The default starting value is
<replaceable class="parameter">minvalue</replaceable>
for ascending sequences and
<replaceable class="parameter">maxvalue</replaceable>
for descending ones.
<comment>
What happens if the user specifies start outside the range?
</comment>
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">cache</replaceable></ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The <option>CACHE <replaceable class="parameter">cache</replaceable></option> 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.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue>CYCLE</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
The optional CYCLE keyword may be used to enable the sequence
to continue when the
<replaceable class="parameter">maxvalue</replaceable> or
<replaceable class="parameter">minvalue</replaceable> has been
reached by
an ascending or descending sequence respectively. If the limit is
reached, the next number generated will be whatever the
<replaceable class="parameter">minvalue</replaceable> or
<replaceable class="parameter">maxvalue</replaceable> is,
as appropriate.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</REFSECT2>
<REFSECT2 ID="R2-SQL-CREATESEQUENCE-2">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Outputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue>CREATE</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
Message returned if the command is successful.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue>ERROR: amcreate: '<replaceable class="parameter"> seqname</replaceable>' relation already exists</ReturnValue>
</TERM>
<LISTITEM>
<PARA>
If the sequence specified already exists.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</variablelist>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
</REFSYNOPSISDIV>
<REFSECT1 ID="R1-SQL-CREATESEQUENCE-1">
<REFSECT1INFO>
<DATE>1998-04-15</DATE>
</REFSECT1INFO>
<TITLE>
Description
</TITLE>
<PARA>
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 <replaceable class="parameter">seqname</replaceable>.
The generator will be "owned" by the user issuing the command.
</PARA>
<para>
After the sequence is created, you may use the function
<function>nextval()</function> with the
sequence name as the argument to get a new number from the sequence.
The function <function>currval('<replaceable class="parameter">sequence_name</replaceable>')</function> may be used
to determine the number returned by the last call to
<function>nextval()</function> for the
specified sequence in the current session.
</para>
<para>
Use a query like
<programlisting>
SELECT * FROM sequence_name;
</programlisting>
to get the parameters of a sequence.
</para>
<para>
Low-level locking is used to enable multiple simultaneous
calls to a generator.
</para>
<REFSECT2 ID="R2-SQL-CREATESEQUENCE-3">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
Notes
</TITLE>
<PARA>
Refer to the DROP SEQUENCE statement to remove a sequence.
</PARA>
<para>
Each backend uses its own cache to store allocated numbers.
Numbers that are cached but not used in the current session will be
lost.
</para>
</REFSECT2>
</refsect1>
<REFSECT1 ID="R1-SQL-CREATESEQUENCE-2">
<TITLE>
Usage
</TITLE>
<PARA>
Create an ascending sequence called serial, starting at 101:
</PARA>
<ProgramListing>
CREATE SEQUENCE serial START 101;
</ProgramListing>
<para>
Select the next number from this sequence
<programlisting>
SELECT NEXTVAL ('serial');
nextval
-------
114
</programlisting>
</para>
<para>
Use this sequence in an INSERT:
<programlisting>
INSERT INTO distributors VALUES (NEXTVAL ('serial'),'nothing');
</programlisting>
</para>
</REFSECT1>
<REFSECT1 ID="R1-SQL-CREATESEQUENCE-3">
<TITLE>
Compatibility
</TITLE>
<PARA>
CREATE SEQUENCE statement is a PostgreSQL language extension.
</PARA>
<REFSECT2 ID="R2-SQL-CREATESEQUENCE-4">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
</REFSECT2INFO>
<TITLE>
SQL92
</TITLE>
<PARA>
There is no CREATE SEQUENCE statement on SQL92.
</PARA>
</refsect2>
</refsect1>
</REFENTRY>
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