Oracle-L: Re: SQL question

From: Ferenc Mantfeld <mantfield_at_connexus.net.au>
Date: Mon, 24 Feb 2003 12:49:55 -0800
Message-ID: <F001.005575CE.20030224124955@fatcity.com>

Why not use a sequence to populate ID, and let it fire of a before insert trigger. code example below:

create sequence TAB1_PKSEQ ;
create or replace trigger test_pkgen
BEFORE INSERT OR UPDATE OF col_id on TABLE_A FOR EACH ROW
BEGIN
IF INSERTING THEN
SELECT TAB1_PKSEQ1.NextVal INTO :new.COL_ID FROM DUAL; /* or something like the above */
END IF;
END;
/

I am assuming you have other columns to populate too, which is not the PK of the table.

Cheers :

Ferenc Mantfeld
Dreaming costs you nothing. Not dreaming costs you everything.

Original Message ----- From: Rick Stephenson To: Multiple recipients of list ORACLE-L Sent: Tuesday, February 25, 2003 6:49 AM Subject: SQL question

OS: Solaris 2.8

Database: Oracle 9.2.0.2

Situation in chronological order

Connection A: select * from table A where id = 1; Result: no rows returned -- This means I need to insert the row, as it does not exists yet.

Connection B: select * from table A where id = 1; Result: no rows returned -- This means I need to insert the row, as it does not exists yet.

Connection A: insert into table A(id) values = 1; Result: 1 row inserted

Connection B: insert into table A(id) values = 1; Result: Unique constraint violated -- This is the problem. How do I avoid this happening?

Question: How can I force connection B to wait for connection A to insert the new row before it does the select?

If I were updating the row, I could use the "for update" clause to force the wait. Is there a clean way to do that for an insert?

Thanks for your help,

Rick Stephenson

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Author: Ferenc Mantfeld
INET: mantfield_at_connexus.net.au

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