Skewness

What is the meaning of skewness in Teradata? When do we use nullif function in Teradata?

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Ajay Sai Veerapaneni

  • Oct 27th, 2010
 

Skewness is the statistical term, which refers to the row distribution on AMPs. If the data is highly skewed, it means some AMPs are having more rows and some very less i.e. data is not properly/evenly distributed. This affects the performance/Teradata's parallelism. The data distribution or skewness can be controlled by choosing indexeswe use nullif when we want to return a null value when the expression in that statement is true.

msrakesh

  • Mar 29th, 2012
 

When we choose wrong primary index the data unevenly distributed across all the amps means some amps have more records and some amps had less records this is called skewness.
Percentage of skewness is called skew factor.30% skew factor is acceptable.

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arunFERGY

  • May 31st, 2017
 

unequal distribution of data on amps is called skewness. Nullif function compares two arguments, if they matches then it returns null else it returns first argument.

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