Re: PRIMARY KEY - Mailing list pgsql-sql
From | M.P.Dankoor |
---|---|
Subject | Re: PRIMARY KEY |
Date | |
Msg-id | 45EEB52F.4080604@gmail.com Whole thread Raw |
In response to | PRIMARY KEY ("Shavonne Marietta Wijesinghe" <shavonne.marietta@studioform.it>) |
List | pgsql-sql |
Phillip Smith wrote: <blockquote cite="mid1173269986.4925.64.camel@phillip-desktop" type="cite"> If you actually need toknow the value of N_GEN in your ASP application, you will need to query the database first and select the NEXTVAL fromthe sequence that the "serial" data type will create, then use that returned value in your insert - ie, DON'T excludeit from the insert, otherwise it will default to NEXTVAL again and return a different value.<br /><br /> The onlycatch with this is that you most likely won't end up with contiguous values in this column - ie, if a user cancels afteryou seect nextval, but before you insert - the value of the sequence has already increased, and will be increased againbefore returning a value when you next select nextval<br /><br /></blockquote><br /> That's precisely why I would notuse the nextval call, you might end up with gaps. Moreover you are making 2 database calls instead of one.<br /> But thenagain, if your application needs to know the value you can't really avoid using nextval (good thing it's concurrencyproof)<br /><br /> Mario<br /><br /><br /> Phillip Smith wrote: <blockquote cite="mid1173269986.4925.64.camel@phillip-desktop"type="cite"> If you actually need to know the value of N_GEN in your ASPapplication, you will need to query the database first and select the NEXTVAL from the sequence that the "serial" datatype will create, then use that returned value in your insert - ie, DON'T exclude it from the insert, otherwise it willdefault to NEXTVAL again and return a different value.<br /><br /> The only catch with this is that you most likely won'tend up with contiguous values in this column - ie, if a user cancels after you seect nextval, but before you insert- the value of the sequence has already increased, and will be increased again before returning a value when you nextselect nextval<br /><br /> Cheers,<br /> ~p<br /><br /> On Wed, 2007-03-07 at 12:57 +0100, M.P.Dankoor wrote:<br /><blockquotetype="CITE"> Hello,<br /><br /> Is it possible to redesign your table as follows:<br /><br /> create table Mod48_00_2007(<br /> ID text,<br /> N_GEN serial not null,<br /> FORMSTORE text,<br /> COD_NOTATIO text,<br /> PA_COGNOME text,<br /> constraint pk_Mod48_00_2007 primary key (N_GEN)<br /> );<br /><br /> Yourinsert simply becomes: </blockquote><blockquote type="CITE"> INSERT INTO MOD48_00_2007 (ID, FORMSTORE, COD_NOTAIO, PA_COGNOME)VALUES ('192168217200737122012', '', '00128', 'DE MARTINIS') </blockquote><blockquote type="CITE"><br /> Do notethat you do not refer to the N_GEN column, it will use the next value, please refer to <a href="http://www.postgresql.org/docs/8.1/interactive/datatype.html#DATATYPE-SERIAL">http://www.postgresql.org/docs/8.1/interactive/datatype.html#DATATYPE-SERIAL</a><br />for more information.<br /><br /> Mario<br /><br /> Shavonne Marietta Wijesinghe wrote: </blockquote><blockquote type="CITE"><blockquotetype="CITE"><font size="2">Hello</font></blockquote></blockquote><blockquote type="CITE"><blockquotetype="CITE"> </blockquote></blockquote><blockquote type="CITE"><blockquote type="CITE"> I have createda table </blockquote></blockquote><blockquote type="CITE"><blockquote type="CITE"> CREATE TABLE MOD48_00_2007( ID text, N_GEN int PRIMARY KEY, FORMSTORE text, COD_NOTAIO text, PA_COGNOME text); </blockquote></blockquote><blockquotetype="CITE"><blockquote type="CITE"> </blockquote></blockquote><blockquote type="CITE"><blockquotetype="CITE"> And i insert the rows via a form in ASP. When the form loads i have a functin that goesand gets the value of the field N_GEN adds 1 to it and shows it to the user. </blockquote></blockquote><blockquote type="CITE"><blockquotetype="CITE"> The problem is when i have 2 users working at the same time. </blockquote></blockquote><blockquotetype="CITE"><blockquote type="CITE"> </blockquote></blockquote><blockquote type="CITE"><blockquotetype="CITE"> For example the last value in my field N_GEN is 2 </blockquote></blockquote><blockquotetype="CITE"><blockquote type="CITE"> When both the users A and B loads the form (ASPpage) it sees N_GEN = 3 :) </blockquote></blockquote><blockquote type="CITE"><blockquote type="CITE"> </blockquote></blockquote><blockquotetype="CITE"><blockquote type="CITE"> So they fill in the form and user A clicks on thebutton OK and the record has been inserted with N_GEN = 3. But when the user B clicks on the button the record is notinserted because it has the same key "3" </blockquote></blockquote><blockquote type="CITE"><blockquote type="CITE"> </blockquote></blockquote><blockquote type="CITE"><blockquote type="CITE"> INSERT INTO MOD48_00_2007 (ID, N_GEN, FORMSTORE,COD_NOTAIO, PA_COGNOME) VALUES ('192168217200737122012', '3', '', '00128', 'DE MARTINIS') </blockquote></blockquote><blockquotetype="CITE"><blockquote type="CITE"> </blockquote></blockquote><blockquote type="CITE"><blockquotetype="CITE"> Is there any way i can do this automatically? i mean maybe i have to use someother propertyinstead of "Primary Key" ?? </blockquote></blockquote><blockquote type="CITE"><blockquote type="CITE"> </blockquote></blockquote><blockquotetype="CITE"><blockquote type="CITE"> Thanks </blockquote></blockquote><blockquote type="CITE"><blockquotetype="CITE"> </blockquote></blockquote><blockquote type="CITE"><blockquote type="CITE"><font size="2">ShavonneWijesinghe</font><br /><br /></blockquote></blockquote><blockquote type="CITE"><br /></blockquote><br /><p><b>*******************Confidentialityand Privilege Notice*******************</b><p>The material contained in this messageis privileged and confidential to the addressee. 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