15.00 - Statistics Attribute Definitions - Teradata Database

Teradata Database SQL Data Definition Language Detailed Topics

Product
Teradata Database
Release Number
15.00
Content Type
Programming Reference
Publication ID
B035-1184-015K
Language
English (United States)

Statistics Attribute Definitions

The following table describes the attributes reported by the HELP STATISTICS (QCD Form) statement:

 

Attribute

Description

                                                                                         Inter-Interval Statistics

 

The following group of columns is reported once per HELP STATISTICS request.

Date

The date on which statistics were last collected.

Time

The time at which statistics were last collected.

Number of Rows

An estimate of the cardinality of the table.

Number of Nulls

An estimate of the number of nulls for the specified column or index.

Number of All Nulls

An estimate of the number of rows containing nulls for all columns of the specified column set or index.

Average AMP RPV

Overall average of the average rows per value from each AMP.

Note that the system collects Average AMP Rows Per Value statistics only for NUSI columns. The value is used to improve nested join costing.

If this is not a NUSI column, the system reports a null.

Number of Intervals

The number of intervals in the frequency distribution histogram containing the column or index statistics.

Number of Unique Values

An estimate of the number of unique values for the column or index.

Numeric

Identifies whether the data type of the column set reported on is numeric or non‑numeric.

  • 0 specifies that the data type is non‑numeric.
  • Non‑zero specifies that the data type is numeric.
  • Sampled

    Identifies whether the statistics were collected from all rows in the table or from a sampled subset.

  • 0 specifies that statistics have been collected on all the rows for the specified table.
  • Nonzero specifies that statistics have been collected on a sampled subset of the rows for the specified table.
  • Sampled Percent

    The approximate percentage of total rows in the table included in the sample.

    Version

    The version number of the statistics structure in effect when the statistics were collected.

    Min Value

    An estimate of the smallest value for the specified column or index in the specified table.

    Mode Value

    An estimate of the most frequently occurring value or values for the column or index in the specified table.

    Mode Frequency

    An estimate of the number of rows having the modal value for the specified column or index in the specified table.

                                                                                            Intra‑Interval Statistics

    The following group of columns is reported for each interval returned by a HELP STATISTICS report. Their definitions vary slightly depending on whether the reported information is for an equal‑height or high‑biased interval.

    See SQL Request and Transaction Processing for more information about interval statistics, particularly for detailed descriptions of equal‑height and high‑biased intervals.

                                                                                      Equal-Height Interval Statistics

    Max Value

    An estimate of the largest value for the column or index in the interval.

    Mode Value

    An estimate of the most frequently occurring value or values for the column or index in the interval.

    Mode Frequency

    An estimate of the number of rows in the interval having its modal value for the column or index.

    Non‑Modal Values

    An estimate of the number of distinct non‑modal values for the column or index in the interval.

    Non‑Modal Rows

    An estimate of the number of rows in the interval with values for the specified column or index.

    This is a measure of the skewness of the distribution of the index or column values within the interval.

                                                                                       High-Biased Interval Statistics

    Max Value

    If two values are stored in the interval, then Max is the value for the second high frequency loner.

    Mode Value

    If two values are stored in the interval, then Mode is the value for the first high frequency loner.

    A maximum of two modal values is stored per interval for a skewed distribution.

    Mode Frequency

    The number of rows in the interval having the modal value.

    Non‑Modal Values

    A code indicating the number of loner values for the interval.

  • -1 specifies that the interval has one loner value.
  • -2 specifies that the interval has two loner values.
  • Non‑Modal Rows

    The number of rows in the interval having the maximum value.