Thread: Triggers to create Tables
hi,
this is the part II of a question i already asked:
i have some tables:
create table css_class(nr int4, classname varchar(50));
create table css_prop(nr int4, name varchar(50), val varchar(50),
classnr int4);
(css_prop.classnr foreign key-> css_class.nr)
i would need a trigger on update and insert who takes all entries from
the tables above and put them into a textfile in the following stype
.n-th_of_css_class {
n-th_of_css_prop.name(*) : n-th_of_css_prop.val(*);
n+1-th_of_css_prop.name(*): [...]
}
.n+1-th_of_css_class { [...]
with other words: i want to create a cascading style sheet out of the
table:
css files look something like that
.cassname {
property1 : value_prop1;
property2 : value_prop2;
[...]
}
[...]
Can anyone help?
a c-function would be ok too (_really_ think that i need one) but the
file has to be created by the database itself.
Idea for the future: whole html pages built out of the databased
resulted by trigger/query combination. (not the question _yet_)
MArtin
I am curious about the cost of triggers. The MySQL guys claim that they are very expensive. But if I want to put a trigger on an "update" for a table so that if changing a "N" to a "Y" in a status variable it'll go update another table, e.g. sort of a foreign key constraint since PostGreSQL doesn't have one, what kind of cost is this for normal operations on that table? (Oh, it will update one single record in that other table, and the key value has a unique index on it, so that should not be a problem). -- Eric Lee Green eric@linux-hw.com http://www.linux-hw.com/~eric Beware of those who would sell you a 7200RPM Quantum as an Enterprise-class hard drive.
>>>>> "d" == derndorfer <Martin> writes:
d> hi,
d> this is the part II of a question i already asked:
d> i have some tables:
d> create table css_class(nr int4, classname varchar(50));
d> create table css_prop(nr int4, name varchar(50), val varchar(50),
d> classnr int4);
d> (css_prop.classnr foreign key-> css_class.nr)
d> i would need a trigger on update and insert who takes all entries from
d> the tables above and put them into a textfile in the following stype
d> .n-th_of_css_class {
d> n-th_of_css_prop.name(*) : n-th_of_css_prop.val(*);
d> n+1-th_of_css_prop.name(*): [...]
d> }
d> .n+1-th_of_css_class { [...]
d> with other words: i want to create a cascading style sheet out of the
d> table:
d> css files look something like that
d> .cassname {
d> property1 : value_prop1;
d> property2 : value_prop2;
d> [...]
d> }
d> [...]
d> Can anyone help?
d> a c-function would be ok too (_really_ think that i need one) but the
d> file has to be created by the database itself.
d> Idea for the future: whole html pages built out of the databased
d> resulted by trigger/query combination. (not the question _yet_)
d> MArtin
I think this is bad idea to build text file every time you change the
tables. What about external program (on C, Perl... etc) what rebuilds,
pehaps incrementally, file(s) with changed data? Or creating style
sheets and html pages 'on the fly' with any cgi-script?
--
Anatoly K. Lasareff Email: tolik@icomm.ru
Senior programmer
Hm,
Stylesheets do not change often, it would be better to read them from
textfile than querying the database at the beginning of each html file
which includes it.
MArtin
"Anatoly K. Lasareff" wrote:
>
> >>>>> "d" == derndorfer <Martin> writes:
>
> d> hi,
> d> this is the part II of a question i already asked:
>
> d> i have some tables:
> d> create table css_class(nr int4, classname varchar(50));
> d> create table css_prop(nr int4, name varchar(50), val varchar(50),
> d> classnr int4);
> d> (css_prop.classnr foreign key-> css_class.nr)
>
> d> i would need a trigger on update and insert who takes all entries from
> d> the tables above and put them into a textfile in the following stype
>
> d> .n-th_of_css_class {
> d> n-th_of_css_prop.name(*) : n-th_of_css_prop.val(*);
> d> n+1-th_of_css_prop.name(*): [...]
> d> }
> d> .n+1-th_of_css_class { [...]
>
> d> with other words: i want to create a cascading style sheet out of the
> d> table:
> d> css files look something like that
>
> d> .cassname {
> d> property1 : value_prop1;
> d> property2 : value_prop2;
> d> [...]
> d> }
> d> [...]
>
> d> Can anyone help?
> d> a c-function would be ok too (_really_ think that i need one) but the
> d> file has to be created by the database itself.
>
> d> Idea for the future: whole html pages built out of the databased
> d> resulted by trigger/query combination. (not the question _yet_)
>
> d> MArtin
>
> I think this is bad idea to build text file every time you change the
> tables. What about external program (on C, Perl... etc) what rebuilds,
> pehaps incrementally, file(s) with changed data? Or creating style
> sheets and html pages 'on the fly' with any cgi-script?
>
> --
> Anatoly K. Lasareff Email: tolik@icomm.ru
> Senior programmer
On Fri, 19 Feb 1999, Eric Lee Green wrote: > I am curious about the cost of triggers. > > The MySQL guys claim that they are very expensive. But if I want to put a Pay now, pay later is more of an issue. Using triggers means you code once and then all accesses use the same rules. If the rules change you change the triggers not every application that accesses the database. The other issue is non-application access to the database. Without triggers anyone that can login to the database can make non-rule changes to the data. Triggers prevent this. This is from a modelling prespective. The actual design of your database my require you to go the low-road to get the performance you need. Though more memory, faster disk subsystems, and a faster CPU should help without going that low-road. Rod -- Roderick A. Anderson raanders@altoplanos.net Altoplanos Information Systems, Inc. Voice: 208.765.6149 212 S. 11th Street, Suite 5 FAX: 208.664.5299 Coeur d'Alene, ID 83814
Hi, I've just started learning PostgreSQL (and SQL in general, really, although I do have some experience with a proprietary RDBMS) and have been wondering how I can page through records in a table or view. I learned about cursors and they solved part of the problem - I created a form with Perl/Tk with buttons to move forward a row and backwards a row and that seems to be fine. There are a couple of features I would like to have that I can't figure out how I'd implement. For example, lets say I want to add a new row to the table. I press an 'Add' button, the form goes blank, and I key in all of the information. I press an 'Update' button and behind the scenes things whirl around and update the record in the database. No problem. But let's say now I want to return the user back to the browsing form and place them on the row they just entered (while still being able to "page" through the rows with the forward and back buttons). I'm stuck. If I create a new cursor, I'm back at the beginning of the table - there doesn't seem to be a way to find a particular row and placing the cursor there after creating the cursor. Any help would be appreciated. (I'd love a link to a good online SQL resource.) Dan
On Mon, 22 Feb 1999, Dan Parker wrote: > I learned about cursors and they solved part of the problem - I created a > form with Perl/Tk with buttons to move forward a row and backwards a > row and that seems to be fine. > > There are a couple of features I would like to have that I can't figure > out how I'd implement. For example, lets say I want to add a new row to > the table. I press an 'Add' button, the form goes blank, and I key in all > of the information. I press an 'Update' button and behind the scenes > things whirl around and update the record in the database. No problem. > But let's say now I want to return the user back to the browsing form and > place them on the row they just entered (while still being able to "page" > through the rows with the forward and back buttons). I'm stuck. If I > create a new cursor, I'm back at the beginning of the table - there > doesn't seem to be a way to find a particular row and placing the > cursor there after creating the cursor. Have you looked at pgAccess yet? It's an application written in Tcl/Tk that allows you to build and administer PostgreSQL databases in a manner very similar to MS-Access (hence the name, I guess...) The author of that software has probably already done a lot of what you are trying to do. It can be found at http://www.flex.ro/pgaccess. I believe there may even be a mailing list for it, but you can definitely get more direct information on the INTERFACES mailing list. Brett W. McCoy http://www.lan2wan.com/~bmccoy ----------------------------------------------------------------------- Love at first sight is one of the greatest labor-saving devices the world has ever seen. ----- BEGIN GEEK CODE BLOCK ----- Version: 3.12 GAT dpu s:-- a C++++ UL++++$ P+ L+++ E W++ N- o K- w--- O@ M-@ !V PS+++ PE Y+ PGP- t++ 5- X+ R+@ tv b+++ DI+++ D+ e>++ h+ r++ y++++ ------ END GEEK CODE BLOCK ------