Collect Statistics on Null | Database Administration | VantageCloud Lake - Collecting Statistics on Null - Teradata VantageCloud Lake

Lake - Database Reference
Deployment
VantageCloud
Edition
Lake
Product
Teradata VantageCloud Lake
Release Number
Published
February 2025
ft:locale
en-US
ft:lastEdition
2025-11-21
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ohi1683672393549.ditamap
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pny1626732985837.ditaval
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ohi1683672393549

When you collect statistics, Vantage records three different null counts: NumNulls, PNullUniqueValueCount, and AllNulls.

  • NumNulls is the number of rows that have a null in at least one field. This includes rows with all fields null.
  • PNullUniqueValueCount is the number of unique values in rows with partial nulls.
  • All-Nulls is the number of rows that have all fields null. For example, in the following table, NumNulls count is 4, All-Nulls count is 2, and PNullUniqueValueCount is 2:
    x        y
------  -------
1        a
?        b
?        ?
4        ?
?        ?

Use the SHOW STATISTICS statement to report the number of nulls after collecting statistics. By considering NumNulls, All-Nulls, and PNullUniqueValueCount counts, Teradata can better estimate the number of unique values in the presence of nulls.