Column Statistics Pane
The Column Statistics pane is displayed on the Access Plan tab in the SQL Optimizer window. It lists information about each column in the object highlighted in the Object Statistics or Index Statistics pane. This information is retrieved from the SYSCAT.COLUMNS catalog view excepted for the Index order statistic, which is obtained from SYSCAT.INDEXCOLUSE catalog view.
The average length of the values in the column.
This information is based on the AVGCOLLEN value for the column in SYSCAT.COLUMNS.
The number of rows in a database table.
This information is based on the COLCARD value for the column in SYSCAT.COLUMNS.
The numerical position of the column in the table or view, beginning at zero.
This information is based on the COLNO value for the column in SYSCAT.COLUMNS.
The name of the column.
This information is based on the COLNAME value for the column in SYSCAT.COLUMNS.
The data type of the column along with the length and scale (if applicable).
This information is based on the TYPENAME, LENGTH and possibly the SCALE value for the column in SYSCAT.COLUMNS.
The column’s default value appropriate for the column’s data type. This value can be the keyword NULL.
This information is based on the DEFAULT value for the column in SYSCAT.COLUMNS.
The second highest value in this column.
This information is based on the HIGH2KEY value for the column in SYSCAT.COLUMNS.
The order of the values in this column within the index. Statistic values include:
|
Value |
Description |
|
Ascending |
Ascending order |
|
Descending |
Descending order |
|
Include |
INCLUDE column (ordering ignored) |
The column’s numerical position within the primary key for the table or view. The value N/A appears if the column is not part of the primary key.
This information is based on the KEYSEQ value for the column in SYSCAT.COLUMNS
The second lowest value in this column.
This information is based on the LOW2KEY value for the column in SYSCAT.COLUMNS.
The number of NULL values in the column.
This information is based on the NUMNULLS value for the column in SYSCAT.COLUMNS.
Indicator as to whether the column can contain a NULL value.
|
Value |
Description |
|
Yes |
The column is nullable. |
|
No |
The column is not nullable. |
The column’s numerical position within the table’s partitioning key for the table or view. The value 0 or NULL is displayed if the column is not part of the partitioning key. Additionally, if the table is a hierarchy table or a subtable in a hierarchy, the value NULL is displayed.
This information is based on the PARTKEYSEQ value for the column in SYSCAT.COLUMNS.
The qualified name of the data type if the type is user defined (or distinct). A user-defined type has a qualified name other than SYSIBM. If the data type is not distinct (that is, its qualified name is SYSIBM), the value No appears.
This information is based on the TYPESCHEMA value for the column in SYSCAT.COLUMNS.