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What is the difference between Global temporary tables and Volatile temporary tables?
Global Temporary tables (GTT) -1. When they are created, its definition goes into Data Dictionary.2. When materialized data goes in temp space.3. thats why, data is active upto the session ends, and definition will remain there upto its not dropped using Drop table statement.If dropped from some other session then its should be Drop table all;4. you can collect stats on GTT.Volatile Temporary tables...
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How teradata makes sure that there are no duplicate rows being inserted when its a SET table?
Teradata will redirect the new inserted row as per its PI to the target AMP (on the basis of its row hash value), and if it find same row hash value in that AMP (hash synonyms) then it start comparing the whole row, and find out if duplicate.If its a duplicate it silently skips it without throwing any error.Cheers,Shilpa