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Re: orace sql query

From: Charles Hooper <hooperc2000_at_yahoo.com>
Date: Sat, 23 Jun 2007 19:10:12 -0700
Message-ID: <1182651012.211599.214990@g4g2000hsf.googlegroups.com>


On Jun 23, 6:18 pm, DA Morgan <damor..._at_psoug.org> wrote:
> Charles Hooper wrote:
> > I am now a bit confused on this topic, or are we reading things
> > differently?
>
> > Create a generic table without a primary key:
> > CREATE TABLE T1 (
> > C1 VARCHAR2(20),
> > C2 VARCHAR2(20));
>
> > Table created.
>
> > Create a unique index on the C1 column of the table:
> > CREATE UNIQUE INDEX IND_T1 ON T1(C1);
>
> > Index created.
>
> > Specify that column C1 is the primary key for T1:
> > ALTER TABLE T1 MODIFY (PRIMARY KEY (C1));
>
> > Table altered.
>
> > Take a look at the indexes for the table:
> > SELECT
> > INDEX_NAME
> > FROM
> > DBA_INDEXES
> > WHERE
> > TABLE_NAME='T1';
>
> > INDEX_NAME
> > ----------
> > IND_T1
>
> > DROP INDEX IND_T1;
>
> > ERROR at line 1:
> > ORA-02429: cannot drop index used for enforcement of unique/primary
> > key
>
> > The above seems to be in agreement with the posts by David
> > Fitzjarrell, Ed Stevens, Frank van Bortel, and the Oracle
> > documentation. Or, is this not a valid test?
>
> > Charles Hooper
> > IT Manager/Oracle DBA
> > K&M Machine-Fabricating, Inc.
>
> I know what the error message says.
>
> And I know what the document Frank posted the link to says.
>
> And until corrected by someone I stand by what I wrote.
>
> Consider this:
>
> SQL> select constraint_name, constraint_type, deferrable
> 2 from user_constraints
> 3 where table_name = 'UCLASS';
>
> CONSTRAINT_NAME C DEFERRABLE
> ------------------------------ - --------------
> PK_UCLASS P DEFERRABLE
> CC_UCLASS_CLASS_NAME C NOT DEFERRABLE
>
> SQL> SELECT index_name, index_type, uniqueness
> 2 FROM user_indexes
> 3 WHERE table_name = 'UCLASS';
>
> INDEX_NAME INDEX_TYPE UNIQUENES
> ------------------------------ --------------------------- ---------
> PK_UCLASS NORMAL NONUNIQUE
>
> SQL> DROP INDEX pk_uclass;
> DROP INDEX pk_uclass
> *
> ERROR at line 1:
> ORA-02429: cannot drop index used for enforcement of unique/primary key
>
> I don't believe a non-unique index is being used for enforcement of
> a unique condition. Any comment Tom? Jonathan? Richard? Howard? Except
> to speed the up the search.
> --
> Daniel A. Morgan
> University of Washington
> damor..._at_x.washington.edu (replace x with u to respond)
> Puget Sound Oracle Users Groupwww.psoug.org

A little more information on Oracle using non-unique indexes to enforce primary keys:
http://asktom.oracle.com/pls/asktom/f?p=100:11:1651918238161457::::P11_QUESTION_ID:2913600659112 "Since version 8.0 with deferrable constraints, we've only needed AN INDEX to enforce uniqueness.
Not a unique index, just an index."

Charles Hooper
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Sat Jun 23 2007 - 21:10:12 CDT

Original text of this message

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