Thread: Triggering a table id from a sequence
My desire is to have a table auto update an "id" sequence on every insert, relieving the front end program of the responsibility. I've never written a trigger. I imagine that there may be a contrib trove of them. There may also be an easier way to approach the problem. Please feel free to refer me to books or web sites. TIA, -- Lan Barnes lan@falleagle.net Linux Guy, SCM Specialist 858-354-0616 Tcl/Tk Enthusiast
I don't believe that you need a trigger to do this. When you create a table that will use an
"id"
sequence, you would simply define its datatype as a serial or bigserial. In the background, it
will automatically create a sequence for you and it will automatical set you id column's default
valve to "nextval("your_new_sequence"). when you insert rows into your new table, simply allow
your table to use its default value to give you the next value in you sequence.
see http://www.postgresql.org/docs/8.1/interactive/datatype.html#DATATYPE-SERIAL for an example.
Regards,
Richard
--- Lan Barnes <lan@falleagle.net> wrote:
> My desire is to have a table auto update an "id" sequence on every
> insert, relieving the front end program of the responsibility.
>
> I've never written a trigger. I imagine that there may be a contrib
> trove of them.
>
> There may also be an easier way to approach the problem. Please feel
> free to refer me to books or web sites.
>
> TIA,
>
> --
> Lan Barnes lan@falleagle.net
> Linux Guy, SCM Specialist 858-354-0616
> Tcl/Tk Enthusiast
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match
>
>
am 10.04.2006, um 16:53:27 -0700 mailte Lan Barnes folgendes:
> My desire is to have a table auto update an "id" sequence on every
> insert, relieving the front end program of the responsibility.
>
> I've never written a trigger. I imagine that there may be a contrib
> trove of them.
>
> There may also be an easier way to approach the problem. Please feel
> free to refer me to books or web sites.
A simple way for this is a RULE. (on insert to <table> do also)
test=# create table foo (id int);
CREATE TABLE
test=# create sequence foo_seq;
CREATE SEQUENCE
test=# create rule foo_rule as on insert to foo do also select nextval('foo_seq');
CREATE RULE
test=# select * from foo_seq ;
sequence_name | last_value | increment_by | max_value | min_value | cache_value | log_cnt | is_cycled |
is_called
---------------+------------+--------------+---------------------+-----------+-------------+---------+-----------+-----------
foo_seq | 1 | 1 | 9223372036854775807 | 1 | 1 | 1 | f | f
(1 row)
test=# insert into foo values (5);
nextval
---------
1
(1 row)
test=# insert into foo values (4);
nextval
---------
2
(1 row)
test=# insert into foo values (3);
nextval
---------
3
(1 row)
test=# select last_value from foo_seq ;
last_value
------------
3
(1 row)
http://www.postgresql.org/docs/8.1/interactive/rules-update.html
HTH, Andreas
--
Andreas Kretschmer (Kontakt: siehe Header)
Heynitz: 035242/47215, D1: 0160/7141639
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