Statistical information is vital for the optimizer when it builds query plans. But collecting statistics can involve time and resources. By understanding and combining several different statistics gathering techniques, users of Teradata can find the correct balance between good query plans and the time required to ensure adequate statistical information is always available.
The following statistics collection recommendations are intended for sites that are on any of the Teradata 13.10 software release levels. Most of these recommendations apply to releases earlier than Teradata 13.10, however some may be specific to Teradata 13.10 only.
EXPLAIN SELECT DISTINCT nupi-column FROM table;
 Collecting PARTITION statistics on tables that have grown supports more accurate statistics extrapolations. Collecting on PARTITION is an extremely quick operation (as long as table is not over-partitioned).
 This is sometimes referred to as a random AMP sample since, in early releases of Teradata, a random AMP was picked for obtaining the sample; however, in current releases, the term dynamic AMP sample is more appropriate.
 Any column which is over 95% unique is considered as a nearly-unique column.
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