Top area of the window
The top area of the Referenced Column Statistics window shows general
information about the column.
The columns in the window show both those statistics that were gathered at
the time of the explain and those that currently exist in the system catalog
tables.
| Note: | Distribution statistics do not appear if they are not available or if they
are not used by the optimization level chosen.
|
Rows in the Referenced Column Statistics window
The following information is contained in the rows of the Referenced Column
Statistics window:
- COLCARD
- The number of distinct values in the column.
- COLNO
- The number of the column in the table.
- TYPE
- The data type of the column. This contains the qualified name of
the data type if it is user-defined.
- LENGTH
- The maximum length of the column data. LENGTH=-1 means that the
maximum length is greater than or equal to 32K. LENGTH=0 means that the
column type is user-defined.
- SCALE
- The number of digits after the decimal point for DECIMAL column
types. SCALE=0 means that the column type is not DECIMAL.
- AVGCOLLEN
- The average length of the column.
- NMOSTFREQ
- The number of most frequent values recorded for column
distribution. The explained value is the actual value; the current
value is the configuration setting.
- NQUANTILES
- The number of quantiles recorded for column distribution. The
explained value is the actual value; the current value is the
configuration setting.
- HIGH2KEY
- The second-highest value in the column.
- LOW2KEY
- The second-lowest value in the column.