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Tera-Tom on Teradata Physical Implementa... > Chapter 13: COLLECT STATISTICS - Pg. 419

Physical Implementation Chapter 13 ­ COLLECT STATISTICS "If you are not true to your teeth they will be false to you." Teradata Certified Dentist I asked my dentist, Do I have to floss all my teeth? He said, No, just the ones you want to keep? Whether the Parsing Engine (PE) is checking a users security rights or if statistics were collected on a table the PE will go to user DBC for the answers. The PE uses statistics to help decide what plan to build so the AMPs can satisfy a user`s query. Before the PE can come up with a plan it wants to know if a table is large, medium, or small. It wants to know about certain columns or indexes. Does a particular column have a lot of duplicates, nulls or are the values unique? Does a particular index unique or non-unique or is the index strongly or weakly selective? These questions are often answered by Collect Statistics.