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Does Oracle retrieve records in the same order they were insterted?

Does Oracle retrieve the records from a table in a same order they were inserted (FIFO), assuming that there is no insertion/deletion/updation of records after the records are inserted first and no ORDER/GROUP BY clause is used while retrieving?

In the following query, will the results display the first 500 records of a table in a way they were inserted?

 
 SELECT * FROM TMP WHERE ROWNUM < 501


Relational database theory does not guarantee ordering of records. So you cannot guarantee that records will come out in the same order that they were entered. If there were no insertions/deletions/updations, then you still cannot guarantee order. The "order" can be thrown out of whack when extents are allocated and other internal operations. It is best to use some sort of time-relative sequence and sorting the data on the sequence.

But if all data fits into one extent, no DML has been performed against the table, and no sorting occurs on the data, then yes, they will come out in the same order.

As for the second part, after you've read the first part of this answer, then yes, this will result in the first 500 records inserted into the table.

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This was last published in March 2002

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