17.10 - Statistics Attribute Definitions - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Definition Language Detailed Topics

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
Publication ID
B035-1184-171K
Language
English (United States)

The following tables describe the attributes reported by the HELP STATISTICS (QCD Form) statement.

Inter-Interval Statistics

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

Attribute Description
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, Equal-Height

The following group of columns is reported for equal-height intervals returned by a HELP STATISTICS report.

For more information about equal-height intervals, see Teradata Vantage™ - SQL Request and Transaction Processing, B035-1142.

Attribute Description
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.

Intra-Interval Statistics,  High-Biased

The following group of columns is reported for high-biased intervals returned by a HELP STATISTICS report.

For more information about high-biased intervals, see Teradata Vantage™ - SQL Request and Transaction Processing, B035-1142.

Attribute Description
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.