Обсуждение: Update and trigger

Hi,<br /><br />I need to increament a counter such as myTable.Counter of type integer everytime myTable.status a
booleancolumn is updated. Can you help me complete this...<br /><br />create trigger counter_trigger after update on
myTable.counter<br /> execute procedure 'BEGIN statement; statement; statement END'<br /><br />Q1- how do I narrow the
eventto "update on a column not a row"<br />Q2- can I just provide an inline procedure for the execute<br /><br
/>Thanks<br/> Medi<br /> 

am  Tue, dem 10.06.2008, um 18:45:51 -0700 mailte Medi Montaseri folgendes:
> Hi,
> 
> I need to increament a counter such as myTable.Counter of type integer
> everytime myTable.status a boolean column is updated. Can you help me complete
> this...
> 
> create trigger counter_trigger after update on myTable.counter
> execute procedure 'BEGIN statement; statement; statement END'

much simpler, use a RULE instead a TRIGGER like my example:

Suppose, i have a table called foo, it contains now:

test=# select * from foo;i
---12
(2 rows)


I create a sequence and a RULE:

test=*# create sequence foo_counter;
CREATE SEQUENCE
test=*# create or replace rule foo_update as on update to foo do also select nextval('foo_counter');
CREATE RULE


And now i do a update on foo:


test=*# update foo set i=2;nextval
---------      1
(1 row)

test=*# update foo set i=3;nextval
---------      2
(1 row)


test=*# select currval('foo_counter');currval
---------      2
(1 row)



Andreas
-- 
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID:   0x3FFF606C, privat 0x7F4584DA   http://wwwkeys.de.pgp.net

Medi Montaseri wrote:
> Hi,
> 
> I need to increament a counter such as myTable.Counter of type integer 
> everytime myTable.status a boolean column is updated. Can you help me 
> complete this...
> 
> create trigger counter_trigger after update on myTable.counter
> execute procedure 'BEGIN statement; statement; statement END'
> 
> Q1- how do I narrow the event to "update on a column not a row"

Use a row-level trigger and test to see if the column of interest has 
been altered. Eg:

IF new.fieldname IS DISTINCT FROM old.fieldname THEN   -- Do the work
END IF;

> Q2- can I just provide an inline procedure for the execute

No, at present you must create a function that returns TRIGGER and then 
use that as the target to execute. At least as far as I know.

--
Craig Ringer

am  Wed, dem 11.06.2008, um  0:54:55 -0700 mailte Medi Montaseri folgendes:
> Thanks...but a difference seems to be that the rule is not specific to update
> on a particular col but any col of a row getting updated...
> 
> Thanks

Okay, but i havn't an idea. A statement level trigger can't see the the
data in NEW and OLD. And a row level trigger fires for every row.


> 
> On Tue, Jun 10, 2008 at 10:21 PM, A. Kretschmer <
> andreas.kretschmer@schollglas.com> wrote:

Please, no silly top posting with fullquote below, i'm reading from top
to bottom.


Andreas
-- 
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID:   0x3FFF606C, privat 0x7F4584DA   http://wwwkeys.de.pgp.net