Re: v$sql - executions vs loads vs invalidations

From: David Fitzjarrell <oratune_at_yahoo.com>
Date: Thu, 3 May 2012 20:07:23 -0700 (PDT)
Message-ID: <1336100843.1725.YahooMailNeo_at_web160901.mail.bf1.yahoo.com>

"eg create table t1 as select * from t2 where 1=2 will create table t1 exactly like t2 including constraints without data in it."  
No, it doesn't -- the constraints such as pk and fk constraints are not replicated to the new table:  

SQL>
SQL> --
SQL> -- Create source table
SQL> -- with a pk constraint
SQL> --
SQL>
SQL> create table yazzoo(
  2          snarm   number primary key,
  3          vlapto  varchar2(40),
  4          orp     number,
  5          klop    date,
  6          bnurt   number

  7  );
 
Table created.
 

SQL>
SQL> --
SQL> -- Verify table and constraint existence
SQL> --
SQL>
SQL> select table_name

  2  from user_tables;
 
TABLE_NAME

---

YAZZOO
 
SQL>
SQL> select constraint_name

  2  from user_constraints
  3  where table_name in ('YAZZOO','GRORT');
 

CONSTRAINT_NAME

---

SYS_C0014690
 

SQL>
SQL> --
SQL> -- Create destination table
SQL> -- See if PK constraint is created
SQL> --
SQL>
SQL> create table grort

  2  as select * From yazzoo where 0 = 1;  
Table created.
 

SQL>
SQL> --
SQL> -- Check for table and constraint existence
SQL> --
SQL>
SQL> select table_name

  2  from user_tables;
 
TABLE_NAME

---

YAZZOO
GRORT
 
SQL>
SQL> select constraint_name

  2  from user_constraints
  3  where table_name in ('YAZZOO','GRORT');
 

CONSTRAINT_NAME

---

SYS_C0014690
 
SQL>
David Fitzjarrell

---

From: Subodh Deshpande <deshpande.subodh_at_gmail.com> To: gerry_at_millerandbowman.com
Cc: oracle_at_dunbar-it.co.uk; oracle-l_at_freelists.org Sent: Thursday, May 3, 2012 8:26 PM
Subject: Re: v$sql - executions vs loads vs invalidations

select schema_name.<table_name>.*, rowid from schema.table_name where 1=0 this will not give error..but will not return any rows too. I had seen many developers using such sentences to create staging/holding tables in oracle 7 and 8 era and also in the era of pb and vb as front end.

eg create table t1 as select * from t2 where 1=2 will create table t1 exactly like t2 including constraints without data in it.

from after 8i, 9i  onwards with introduction of global temporary tables, external tables, mviews, and sub queries, I think use of such create statements can be or should be minimised..

thanks...subodh

On 2 May 2012 17:07, Gerry Miller <gerry_at_millerandbowman.com> wrote:

>  Evening Norman,
> I suspect you are correct.
>
> Regards
>
> Gerry
>
>
> Norman Dunbar wrote: Morning Gerry, On 02/05/12 08:31, Gerry Miller wrote:
> AsI mentioned in my reply to Carlos, there are over 6000 such queries in
> theshared pool, each with the structure:
> SELECT<schema_name>.<table_name>.*,
> rowid from<schema>.<table_name> WHERE1=0; I think I should quiz the
> developers as to what they are trying to do with these queries. I've seen
> something like that before. I used to work in a software house where
> Uniface
> was the development tool of choice. It was diabolical, but excellent for
> "database agnostic" applications as it used the best of each database.
> Anyway, before a "table" could be used, it had to be "opened". The query
> there was "select * from schema.table" which was parsed only, but never
> executed. If the parse failed, then the table probably didn't exists and
> the
> application would report a problem. I suspect your queries above are
> something similar? Cheers, Norm.
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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Received on Thu May 03 2012 - 22:07:23 CDT