Oracle-L: RE: SQL Query

From: Bellow, Bambi <bbellow_at_chi.navtech.com>
Date: Fri, 14 Nov 2003 13:54:25 -0800
Message-ID: <F001.005D6B2E.20031114135425@fatcity.com>

Jared --

That is expected behavior for this query. What was weird is that I expected the aggregation in the group by to apply to multiple fileids making GROUP BY a.tablespace_name, b.tablespace_name to be able, then, to join a.tablespace_name to b.tablespace_name as a 1-1 join rather than a many-many. I could have sworn that has worked in the past, but, regardless, my other query returns what I need and the mystery is solved so I don't really need to pursue this with Oracle as a bug... and who really wants to start a bug report on a Friday afternoon for something wimpy?

Hope you have a great weekend!
Bambi.

-----Original Message-----
Sent: Friday, November 14, 2003 2:54 PM
To: Multiple recipients of list ORACLE-L

You can't join DBA_EXTENTS and DBA_DATA_FILES based on an equality of tablespace_name, and then add up the bytes of the files for the tablespace.

ie.

select

b.tablespace_name,
b.bytes
from dba_extents a, dba_data_files b
where a.tablespace_name=b.tablespace_name

Try running that query, and it may become clear.

Your first query correctly aggregates the file sizes.

The second query determines tablespace size based on the number of extents allocated to it.

Drop all the objects in the tablespace, and your tablespace will no longer appear to have any space.

HTH Jared

"Bellow, Bambi" <bbellow_at_chi.navtech.com> Sent by: ml-errors_at_fatcity.com

11/14/2003 09:44 AM
Please respond to ORACLE-L

        
        To:        Multiple recipients of list ORACLE-L
<ORACLE-L_at_fatcity.com> 
        cc:         
        Subject:        SQL Query

Friends --

Why would these two queries return different results?

This query works.

SQL> l
1 select
a.tablespace_name,megs_allocated,megs_used,round(megs_used/b.megs_allocated, 2)*100 pct
2 from (select tablespace_name,sum(bytes)/(1024*1024) megs_used 3 from dba_extents group by tablespace_name) a, 4 (select tablespace_name,sum(bytes)/(1024*1024) megs_allocated 5 from dba_data_files group by tablespace_name) b 6 where a.tablespace_name=b.tablespace_name 7* and a.tablespace_name='NAUAT'
SQL> /

TABLESPACE_NAME                MEGS_ALLOCATED  MEGS_USED        PCT
------------------------------ -------------- ---------- ----------
NAUAT                                22924.25      11509         50

This query does not work

1 select a.tablespace_name,sum(b.bytes)/(1024*1024) megs_allocated, 2 sum(a.bytes)/(1024*1024) megs_used,
3 round(sum(a.bytes)/sum(b.bytes),4)*100 pct 4 from dba_extents a, dba_data_files b 5 where a.tablespace_name=b.tablespace_name 6 and a.tablespace_name='NAUAT'
7* group by a.tablespace_name,b.tablespace_name SQL> /

TABLESPACE_NAME                MEGS_ALLOCATED  MEGS_USED        PCT
------------------------------ -------------- ---------- ----------
NAUAT                              31773010.5      23018        .07

Bambi.
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Author: Bellow, Bambi
INET: bbellow_at_chi.navtech.com

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Author: Bellow, Bambi
INET: bbellow_at_chi.navtech.com

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