Archives of the TeradataForum
Message Posted: Fri, 09 Dec 2005 @ 15:08:46 GMT
| Subj: | | Re: How sample works? |
| |
| From: | | Dieter Noeth |
Zdravko Sonje wrote:
| | Can someone explain how "sample" works? | |
| | Explain for "select * from table1 sample 100" says: | |
> (all_amps), which is built locally on the AMPs. The
> result spool file will not be cached in memory. The
> size of Spool 3 is estimated with low confidence to be
> 11,767,538 rows. The estimated time for this step is
> 3 hours and 58 minutes.
This is probably not the sample step, it should look like:
3) We do an all-AMPs SAMPLING step from .... by
way of an all-rows scan with no residual conditions
into Spool 1 (group_amps), which is built locally on the
AMPs. Samples are specified as a number of rows.
| | Table table1 has 300 m records and I need only 100 records. What is the trick? | |
As long as it's really just a "select * from table sample x;" (and your system is not a large one) this is supposed to be fast.
If you don't want a real sample, but just want to see some data and you're already on V2R6 use Microsoft syntax instead:
select top 100 * from table;
Dieter
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