Re: Randomize data from SQL statement
Tricia Kha wrote
>I want to generate a 30% random sample output data from my
>Order_number field of my Order_item table.
A quick trick someone posted here before:
select *
from all_tables
where dbms_utility.get_hash_value( dump( rowid ), 0, 100 ) <= 30;
If I am correct, then get_hash_value is available as of version 7.3 (it is
not in PO7.2). This will get you the same 30% every time you run the query.
You might add sysdate to get different (though not truly random at all)
results:
select *
from all_tables
where dbms_utility.get_hash_value( dump( rowid ) + sysdate, 0, 100 ) <=30;
Better, get the Rand function at
http://www.oracle.com/st/products/features/free_plsql_utilities.html
select *
from all_tables
where Rand < 0.30;
Note that in neither case you can be sure that indeed exactly 30% is
retrieved.
Arjan.
I have sent a CC: to your mail address, as my posts are not always visible
in all newsgroups :-(