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How is ROWID generated?
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Message Score Author Date
Hi All: I ain't a DBA bt I wanna know how is RO...... Omar Faruque Jan 07, 2008, 08:39
Hi, Gather row+block+file+segment info then get...... Vinnie G Jan 07, 2008, 09:45
Thanks dragondb. Omar.... Omar Faruque Jan 07, 2008, 10:05
Hello Omar, more information, explanations, exa...... Score: 100 PtsScore: 100 PtsScore: 100 PtsScore: 100 PtsScore: 100 Pts Bruno Vroman Jan 07, 2008, 11:13
Hi Bruno: Tnx 4 ur suggestion. I'll go through ...... Omar Faruque Jan 07, 2008, 12:08
Hi Omar, here are some more facts from my side:- ...... Score: 200 PtsScore: 200 PtsScore: 200 PtsScore: 200 PtsScore: 200 Pts Amar Kumar Padhi Jan 07, 2008, 13:59
One addition to the above response. Extended ROWID...... Amar Kumar Padhi Jan 07, 2008, 14:08
SYSDATE is not a pseudo-column it is a function E...... Michel Cadot Jan 07, 2008, 14:13
Hi Michael, thanks for the correction. >SYSDAT...... Amar Kumar Padhi Jan 07, 2008, 16:51

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Subject: How is ROWID generated?
Author: Omar Faruque, Bangladesh
Date: Jan 07, 2008, 08:39, 2958 days ago
Message: Hi All:

I ain't a DBA bt I wanna know how is ROWID generated?

Please help me.

Omar.
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Subject: Re: How is ROWID generated?
Author: Vinnie G, China
Date: Jan 07, 2008, 09:45, 2958 days ago
Message: Hi,

Gather row+block+file+segment info then get rowid ;
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Subject: Re: How is ROWID generated?
Author: Omar Faruque, Bangladesh
Date: Jan 07, 2008, 10:05, 2958 days ago
Message: Thanks dragondb.

Omar.
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Subject: Re: How is ROWID generated?
Author: Bruno Vroman, Belgium
Date: Jan 07, 2008, 11:13, 2958 days ago
Score:   Score: 100 PtsScore: 100 PtsScore: 100 PtsScore: 100 PtsScore: 100 Pts
Message: Hello Omar,

more information, explanations, examples in Oracle documentation...
The ROWID depends on the Oracle version that you use, but for example here are two entries listed when searching for ROWID in Oracle 10g documentation;

http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/pseudocolumns008.htm#sthref828

http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/datatype.htm#sthref3894

Even if you are not a DBA, I suggest you to have a look at the Oracle Documentation (start with "Concepts"); you will for sure find a lot of very interesting things!

Good reading,

Bruno Vroman.
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Subject: Re: How is ROWID generated?
Author: Omar Faruque, Bangladesh
Date: Jan 07, 2008, 12:08, 2958 days ago
Message: Hi Bruno:

Tnx 4 ur suggestion. I'll go through d doc. Actually I'm a developer & now trying 2 learn administrative parts.

Omar.
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Subject: Re: How is ROWID generated?
Author: Amar Kumar Padhi, United Arab Emirates
Date: Jan 07, 2008, 13:59, 2958 days ago
Score:   Score: 200 PtsScore: 200 PtsScore: 200 PtsScore: 200 PtsScore: 200 Pts
Message: Hi Omar,
here are some more facts from my side:-
- ROWID is a pseudo column, just like SYSDATE.

- It denotes the exact position on the disk where the required data is lying.

- It is not stored with the table but if the table has index it would be stored for data satisfying the indexed column(s).

- Data access by ROWID is the fasted mechanism of data retrieval. As this is stored in indexes, they improve SQL performance as the exact position on disk is available for reading (well yes, it also depends on how the indexes are being used and if the execution plan is optimal!).

- The actual format of ROWID is <Object number-relative file number-Block number-Row number>, this is represented in a ROWID as OOOOOOFFFBBBBBBRRR (numbers 6,3,6,3). This is the Extended ROWID format that is visible in 9i and above version.

- The ROWID format mentioned above changes for a BigFile tablespace, introduced in 10g. The format becomes <Object number-encoded Block number-Row number>, this is represented as OOOOOO-LLLLLLLLL-RRR (numbers 6,9,3).

Thanks!
amar
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Subject: Re: How is ROWID generated?
Author: Amar Kumar Padhi, United Arab Emirates
Date: Jan 07, 2008, 14:08, 2958 days ago
Message: One addition to the above response. Extended ROWID is available from Oracle 8i. The ROWID format prior to this version is know as Restricted ROWID now.

Thanks!
amar
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Subject: Re: How is ROWID generated?
Author: Michel Cadot, France
Date: Jan 07, 2008, 14:13, 2958 days ago
Message: SYSDATE is not a pseudo-column it is a function
Extended ROWID was available since 8.0 not 8i or 9i.
In OOOOOOFFFBBBBBBRRR and OOOOOO-LLLLLLLLL-RRR each element is not number in the sense of decimal number it is a 64-base number.

Regards
Michel
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Subject: Re: How is ROWID generated?
Author: Amar Kumar Padhi, United Arab Emirates
Date: Jan 07, 2008, 16:51, 2958 days ago
Message: Hi Michael,
thanks for the correction.

>SYSDATE is not a pseudo-column it is a function
Yes you are right, I actually meant to say "ROWNUM" in the first place.

> Extended ROWID was available since 8.0 not 8i or 9i.
I personally did not remember this, thanks anyway.

> In OOOOOOFFFBBBBBBRRR and OOOOOO-LLLLLLLLL-RRR each element is not number in the sense of decimal number it is a 64-base number.
I never said it is decimal number, but it will be Fyi for the original poster.

Omar, you can further select the rowid on a table and check on its format.


Thanks!
amar
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