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The Oracle ORDER BY Clause [Return To Index]

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Term: ORDER BY

Definition:
The Oracle ORDER BY clause specifies the sorting, or order, that rows are returned in from a query.

The ORDER BY clause always uses a parameter that tells the database how to sort the returned rows. Valid parameters are ASC or DESC. These specify ascending order and descending order.

The ASC parameter
The DESC parameter

Random Ordering
To order rows randomly, you must use DBMS_RANDOM, as shown here:

SELECT column FROM

( SELECT column FROM table

ORDER BY dbms_random.value )

WHERE rownum = 5

In the example above, 5 randomly selected rows will be returned.

You can also get a random sample, by using the SAMPLE clause with a SELECT statement:

SELECT * FROM users SAMPLE(15);

In the example above, Oracle is instructed to randomly return 15% of the rows in the 'users' table. Note that the SAMPLE clause only works for single table queries on local tables.

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