How does Oracle extract records in physical order? (from Itpub)

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How do I extract records in physical order?
Rt
SELECT * from TabName and select/*+first_rows*/from TabName?
Thank you


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04-08-13 18:24 Qinhuai Night Moon
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What is the physical order?
is the order in the block? or the chronological order in which the records are generated?


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04-08-13 22:36 Li2
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There is a problem, if it is a parallel query, query merging is not also in the physical order?


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04-08-14 10:16 x_x
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Quote: Originally released by Qinhuai Night Month
What is the physical order?
is the order in the block? or the chronological order in which the records are generated?
Should be the chronological order in which records are produced
In fact, what I want to ask is, is the order of the data in the select * from TabName the same in the order in which they were taken?



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04-08-14 10:53 Qinhuai Night Moon
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Quote: Originally released by X_x

Should be the chronological order in which records are produced
In fact, what I want to ask is, is the order of the data in the select * from TabName the same in the order in which they were taken?



I feel that the select * from table is scanned by block (not validated by experiment, but from an efficiency standpoint), because the records inserted later may use the space in front of the delete, so this is not necessarily the chronological order.
In fact, relational databases all emphasize physical independence, all operations only guarantee the logical layer, if you want to extract the row in chronological order, it is best to add a column to record the generation time of the line



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04-08-14 13:21 Grassbell
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Quote: Originally released by Qinhuai Night Month




I feel that the select * from table is scanned by block (not validated by experiment, but from an efficiency standpoint), because the records inserted later may use the space in front of the delete, so this is not necessarily the chronological order.
In fact, relational databases all emphasize physical independence, all operations only guarantee the logical layer, if you want to extract the row in chronological order, it is best to add a column to record the generation time of the line

SELECT * FROM table returns the order of values:

Rows in the same block are read in the order in which row is arranged in the row dictionary of the block header. Delete and then insert, then the row may use the deleted row in the row dictionary position.

But the order between blocks, I presume, is in the order of blocks in segment.



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04-08-14 16:03 Grassbell
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can refer to:

Http://www.itpub.net/112239.html

Http://www.itpub.net/247459.html


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