Q:

Efficiency of top vs. sample in Teradata

In Teradata, which is more efficient - Sample or Top? Since sample is random, does that cause Teradata to do less work and result in faster returns? 
Routinely, I just want to see a few rows. 
Thread related:
differences between top and sample in teradata sql

A:

I just ran three queries on a large Teradata dataset:  

SELECT * FROM table Sample 10;
SELECT * Top 10 FROM table; (with no order by)
SELECT * Top 10 FROM table ORDER BY column;

The DBQL metrics show that by far, the Top 10 with no order is the least resource-intensive.  I had about a 99% drop in I/O & CPU just changing from SAMPLE to TOP. 
So if your goal is purely efficiency, then TOP without the Order by is the clear winner going by TD's DBQL metrics.  

